Force determination employing sheet sensor and capacitive array

ABSTRACT

A device configured to sense a touch on a surface of the device. The device includes a cover and a force-sensing structure disposed below the cover. The force-sensing structure may be positioned below a display and used in combination with other force-sensing elements to estimate the force of a touch on the cover of a device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 14/727,601, filed Jun. 1, 2015, and titled “Force Determination Employing Sheet Sensor and Capacitive Array,” now U.S. Pat. No. 10,048,789, which is a continuation of U.S. patent application Ser. No. 14/619,807, filed Feb. 11, 2015, and titled “Force Determination Employing Sheet Sensor and Capacitive Array,” now abandoned, which claims priority to U.S. Provisional Patent Application No. 62/047,645, filed Sep. 8, 2014, and titled “Force Determination Employing Sheet Sensors and Capacitive Array,” U.S. Provisional Patent Application No. 61/941,988, filed Feb. 19, 2014, and titled “Force Determination Employing Sheet Sensors and Capacitive Array,” and U.S. Provisional Patent Application No. 61/939,252, filed Feb. 12, 2014, and titled “Force Determination Employing Multiple Force-Sensing Structures,” the disclosure of each of which is incorporated by reference in its entirety.

TECHNICAL FIELD

This application generally relates to systems and methods sensing the force of a touch, and in particular to a capacitive force sensor integrated with a device for detecting and measuring the amount or magnitude of a touch applied to a surface of the device.

BACKGROUND

Touch devices can be generally characterized as devices that are capable of receiving touch input on the surface of the device. The input may include the location of one or more touches on the device, which may be interpreted as a command, gesture, or other type of user input. In one example, touch input on a touch device may be relayed to an a computing system and used to interpret user interaction with a graphical user interface (GUI), including, for example, selecting elements on a display, reorienting or repositioning elements on a display, entering text, and user input. In another example, touch input on a touch device may be relayed to a computer system and used to interpret a user's interaction with an application program. The user's interaction may include, for example, the manipulation of audio, video, photographs, presentations, text, and the like.

Typically, touch input on a touch device is limited to the location of a touch on the device. However, in some cases, it may be advantageous to also detect and measure the force of a touch that is applied to the device. For example, it might be advantageous for a user to be able to manipulate a computer-generated object on a display in a first way using a relatively light touch and, alternatively, interact with the object a second way using a relatively heavy or sharper touch. By way of example, it might be advantageous for a user to move a computer-generated object on the display using a relatively light touch and then, alternatively, select or invoke a command with respect to the same computer using a relatively heavy or sharper touch. More generally, it might be advantageous for the user to be able to provide input in multiple ways depending on the force of the touch. For example, a user may provide input that is interpreted a first way for a light touch, a second way for a medium touch, and a third way for a heavy touch, and so on. Additionally, it might be advantageous for the user to be able to provide an analog input using a varying amount of force. This type of input may be useful for controlling, for example, a gas pedal on a simulated car or a control surface of an airplane in a flight simulator, or similar applications. It may be further advantageous for the user to be able to provide input, such as simulated body movements or otherwise, in a virtual reality (VR) simulation (possibly with haptic feedback), or in an augmented reality program. It might be further advantageous to use the force of a touch to interpret the relative degree (e.g., force) and locations of multiple touches that are provided to multiple user interface objects or elements that are in use on a touch device at the same time. For example, the force of a touch could be used to interpret multiple touches due to a user pressing more than one element in an application for playing a musical instrument. In particular, the force of multiple touches may be used for interpreting multiple touches by a user on the keys of a piano. Similarly, the force of multiple touches can be used to interpret a user's multiple touches in an application for controlling a motor vehicle (having separate controls for accelerating, braking, signaling, and turning).

SUMMARY

This application provides techniques, which can be used to measure or determine the amount or magnitude of force applied, and changes in the amount or magnitude of force applied, by a user contacting a touch device (such as a touch-sensitive surface, one example of which is a touch display), or other pressure-sensitive input elements (such as a virtual analog control or keyboard), or other input device. These techniques can be incorporated into various devices using touch recognition, touch elements of a GUI, and touch input or manipulation in an application program, such as touch devices, touch pads, and touch screens. This application also provides systems and techniques that can be used to measure or determine the amount or magnitude of force applied, and changes in the amount or magnitude of force applied, by the user when contacting a touch device, and in response thereto, provide additional functions available to a user of a touch device.

Certain embodiments described herein are directed to a force sensor, also referred to as a “force-sensing structure” or a “force sensitive sensor.” The force sensor may be integrated with the housing of an electronic device, one example of which is a touch sensitive electrical device or simply a touch device. A sample force sensor may include an upper portion and a lower portion separated by a compressible element or by an air gap. The upper portion may include an upper body connected to an upper capacitive plate and the lower portion may include a lower body connected to a lower capacitive plate. In some cases, the upper portion and the lower portion form a capacitor that can be used to measure or detect an amount or magnitude of applied force. The compressible element is typically formed form a compliant or springy material. In some cases, the compressible element is referred to as a “deformable middle body,” an intermediate element, or a “compressible layer.” In some cases, the force sensor includes other force-sensing elements, such as a resistive strain gauge, piezoelectric element, and the like.

Some example embodiments are directed to an electronic device having a cover, a display positioned below the cover, and a force-sensing structure disposed below the display. The force-sensing structure may include an upper capacitive plate, a compressible element disposed on one side of the upper capacitive plate, and a lower capacitive plate disposed on a side of the compressible element that is opposite the upper capacitive plate. The force-sensing structure may also include a plate affixed to and supporting the force-sensing structure. In some embodiments, the electronic device also includes sensing circuitry that is operatively coupled to the force-sensing structure. The sensing circuitry may be configured to estimate the force of a touch on the cover based on a change in capacitance between the upper capacitive plate and the lower capacitive plate of the force-sensing structure.

In some embodiments, the force-sensing structure is separated from the display by a compliant layer including an air gap. In some cases, the force-sensing structure is separated from the display by a compliant layer comprised of compressible foam. The force-sensing structure may be separated from the display by a compliant layer comprised of an array of compliant pillars and an optically transparent fluid.

In some embodiments, the electronic device also includes a housing having a bezel surrounding the cover and a gasket disposed in a gap between the cover and the bezel. The device may also include an oleophobic coating disposed over at least a portion of the gap.

Some example embodiments are directed to an electronic device including a housing, a cover disposed within an opening of the housing, and a strain-sensitive gasket disposed between the cover and the housing along a perimeter of the cover. The device may also include a force-sensing structure disposed below the cover. The device may also include a plate fixed relative to the housing and supporting the force-sensing structure. In some cases, the strain-sensitive gasket includes a gasket upper capacitive plate, a gasket lower capacitive plate, and a gasket compressible element disposed between the gasket upper capacitive plate and the gasket lower capacitive plate.

In some embodiments, the electronic device also includes a display disposed between the cover and the force-sensing structure, and a compressible layer comprising an air gap between the display and the force-sensing structure. In some implementations, the air gap of the compressible layer is configured to at least partially collapse in response to a force of a touch that exceeds a first threshold. The first threshold may be less than a second threshold that corresponds to a maximum force that can be detected by the strain-sensitive gasket.

In some embodiments, the electronic device also includes a display disposed between the cover and the force-sensing structure, and a compressible layer between the display and the force-sensing structure. In some cases, the compressible layer may be configured to at least partially collapse in response to a force of a touch that exceeds a first threshold. The first threshold may be less than a second threshold that corresponds to a maximum force that can be detected by the strain-sensitive gasket.

In some embodiments, the force-sensing structure includes: an upper capacitive plate, a lower capacitive plate; and a compressible element disposed between the upper capacitive plate and the lower capacitive plate. In some embodiments, the force-sensing structure includes a strain gauge and/or a piezoelectric element.

Some example embodiments are directed to an electronic device including a cover, a capacitive sense layer positioned below the cover, and a compressible layer below the capacitive sense layer. In some embodiments, the compressible layer comprises an air gap. The electronic device may also include a force-sensing structure disposed below the compressible layer, which includes an upper capacitive plate, a compressible element disposed on one side of the upper capacitive plate, and a lower capacitive plate disposed on a side of the compressible element that is opposite the upper capacitive plate. Some embodiments include a plate positioned below the force-sensing structure and supporting the force-sensing structure.

In some embodiments, the electronic device includes a display positioned below the cover. The device may also include a backlight positioned below the display. The capacitive sense layer may be disposed between the display and the backlight.

In some embodiments, the electronic device includes sensing circuitry that is operatively coupled to the capacitive sense layer and the force-sensing structure. The sensing circuitry may be configured to estimate the force of a touch on the cover based on a change in mutual capacitance between the capacitive sense layer and the upper capacitive plate of the force-sensing structure. In some embodiments, the sensing circuitry may be configured to obtain a first capacitance between the upper capacitive plate and the lower capacitive plate of the force sensing structure. The circuitry may also be configured to obtain a second capacitance between the upper capacitive plate and the capacitive sense layer. The circuitry may also be configured to generate an estimate of a force of a touch on the cover using the first and second capacitances.

While multiple embodiments are disclosed, including variations thereof, still other embodiments of the present disclosure will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the disclosure. As will be realized, the disclosure is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present disclosure. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example touch device.

FIG. 2A depicts a cross-sectional view taken along line 1-1 of FIG. 1, of an example touch device having a force-sensing structure.

FIG. 2B depicts a cross-sectional view taken along line 1-1 of FIG. 1, of an example touch device having an alternative force-sensing structure.

FIG. 3 depicts a cross-sectional view taken along line 2-2 of FIG. 2, of an example touch device having a force-sensing structure.

FIG. 4 depicts a cross-sectional view taken along line 2-2 of FIG. 2, of an example touch device having a force-sensing structure.

FIG. 5 depicts a cross-sectional view taken along line 2-2 of FIG. 2, of an example touch device having a force-sensing structure.

FIG. 6 depicts a cross-sectional view of an embodiment of a touch device having a capacitive force sensor.

FIG. 7 depicts another embodiment of a touch device having a capacitive force sensor.

FIG. 8 depicts a cross sectional view of another embodiment of a touch device having a capacitive force sensor.

FIG. 9 depicts an exemplary communication between a touch I/O device and a computing system.

FIG. 10 depicts a schematic of a system including a force sensitive touch device.

FIG. 11A depicts an example method of operation.

FIG. 11B depicts another example method of operation.

FIG. 12 depicts a force-sensitive structure having an electrical connector tail.

FIG. 13 depicts a cross-sectional view of an electrical connector tail.

FIG. 14 depicts an example method of manufacturing a force-sensitive structure having an electrical connector tail.

FIG. 15A depicts a sample cross-section of another force-sensitive structure incorporated into an electronic device.

FIG. 15B depicts a sample cross-section of still another force-sensitive structure incorporated into an electronic device.

FIG. 15C depicts a sample cross-section of yet another force-sensitive structure incorporated into an electronic device.

FIGS. 15D-E depict a portion of the cross-section of FIG. 15C in greater detail.

FIG. 16 depicts a sample cross-section of an electronic device incorporating two force-sensitive structures.

FIG. 17 depicts a sample cross-section of an electronic device incorporating a multi-layered sheet force sensor, coupled with a capacitive sensing array positioned in a display stack.

DETAILED DESCRIPTION

Generally, embodiments may take the form of an electronic device capable of sensing force and distinguishing between multiple different levels of force, beyond simple binary sensing. Some embodiments may have an enclosure incorporating a force sensor therein (e.g., a force-sensitive sensor, a force-sensing element, or force-sensing structure). The force sensor may be incorporated in, for example in a groove, cutout, or aperture formed in one or more sidewalls or other surfaces of the device. The force-sensing element may extend along an entire periphery, sidewall, or set of sidewalls in certain embodiments. For example, the force sensor may encircle an interior cavity formed within the device, or may otherwise extend around an interior of the device. As force is exerted on an exterior of the device, such as an upper surface, the force sensor may detect the force and generate a corresponding input signal to the device.

Some embodiments may incorporate multiple force sensors spaced about a perimeter of the electronic device, rather than a single force-sensing structure or element. Further, the multiple force sensors need not form a continuous array or structure, but may be discretely spaced from one another. The number of force sensors may vary between embodiments, as may the spacing. Each force sensor may sense a force exerted on an adjacent or nearby surface within a certain region of the device. Thus, a force exerted at a point that is between two underlying force sensors may be sensed by both.

Generally, the force sensor or device may include one or more capacitive plates, traces, flex, or the like that are separated by a compressible element (e.g., a compliant member). As a force is transmitted through the device enclosure and to the force sensor, the compressible element may compress, thereby bringing the capacitive plates closer together. The change in distance between the capacitive plates may increase a measured capacitance therebetween. A circuit may measure this change in capacitance and output a signal that varies with the change in capacitance. A processor, integrated circuit or other electronic element may correlate the change in capacitance to a force exerted on the enclosure, thereby facilitating the detection, measurement, and use of force as an input to an electronic device. Although the term “plate” may be used to describe the capacitive elements, it should be appreciated that the capacitive elements need not be rigid but may instead be flexible (as in the case of a trace or flex).

1. Terminology

The following terminology is exemplary, and not intended to be limiting in any way.

The text “applied force”, and variants thereof, generally refers to the force of a touch applied to a surface of the device. Generally, the degree, amount, or magnitude of the applied force can be detected and measured using the techniques described herein. The degree, amount, or magnitude of an applied force need not have any particular scale. For example, the measure of applied force can be linear, logarithmic, or otherwise nonlinear, and can be adjusted periodically (or otherwise, such as aperiodically, or otherwise from time to time) in response to one or more factors, either relating to applied force, location of touch, time, or otherwise.

The text “finger”, and variants thereof, generally refers to a user's finger, or other body part. For example and without limitation, a “finger” can include any part of the user's finger or thumb and any part of the user's hand. A “finger” may also include any covering on the user's finger, thumb, or hand.

The text “touch,” and variants thereof, generally refers to the act of an object coming into contact with a surface of a device. The object may include a user's finger, a stylus or other pointing object. Example objects include, a hard stylus, a soft stylus, a pen, finger, thumb or other part of the user's hand. A “touch” typically has an applied force and a location that can detected and measured using the techniques described herein.

After reading this document, those skilled in the art would recognize that these statements of terminology would be applicable to techniques, methods, physical elements, and systems (whether currently known or otherwise), including extensions thereof inferred or inferable by those skilled in the art after reading this application. Likewise, it should be appreciated that any dimensions set forth herein are meant to be examples only, and may change from embodiment to embodiment.

2. Force-Sensitive Device

In one embodiment, a force sensitive device and system can include a cover glass element, such as a relatively transparent (in most or all locations) substance capable of isolating circuitry or other internal elements of the touch device from external objects. The term “glass” refers to the relatively hard sheet-like qualities of the material and does not limit the material of the cover glass element to only glass materials. The cover glass element may be made from a variety of materials including, for example, glass, treated glass, plastic, treated plastic, and sapphire. In many cases, the cover glass is transparent, however it is not necessary that the cover glass be completely or even partially transparent. The cover glass can be disposed in a substantially rectilinear shape, such as to cover the circuit for the touch device and to serve as a touch plate for the user. The cover glass may also be formed in a variety of other shapes depending on the application.

In some embodiments, the cover glass is integrated with or attached to a transparent or non-transparent touch sensor that is configured to detect the location of a touch. The transparent touch sensor may be a capacitive touch sensor formed from one or more arrays of transparent conductive lines. For example, the transparent touch sensor may be a mutually capacitive touch sensor formed from two arrays of transverse transparent conductive lines operatively coupled to touch sensing circuitry. Such a transparent touch sensor may be able to detect and track multiple touches on the surface of the cover glass. The touches may include multiple finger touches, multiple stylus touches, or a combination of different types of touches on the cover glass. Other types of transparent touch sensors may also be used, including, for example, self-capacitive touch sensors, resistive touch sensors, and the like.

In one embodiment, the cover glass element is coupled to a frame or housing for the touch device, such as a case constructed of metal, elastomer, plastic, a combination thereof, or some other substance. In such cases, the frame for the touch device can include a shelf or ledge on which the cover glass element is positioned. The cover glass is typically positioned above the circuitry for the touch device. For example, the frame can include a shelf on which an edge of the cover glass element is positioned, with the (or some of the) remainder of the cover glass element positioned over the circuitry for the touch device.

In many of the embodiments described herein, a force sensor, (e.g. a force-sensing structure, force-sensing element, or force sensitive sensor), is positioned below the cover glass and the shelf or ledge of the frame or housing. The force sensor typically includes a compressible element and is configured to detect and measure a relative displacement between the cover glass and the frame or housing. As previously mentioned, the amount that the cover glass is displaced can be used to estimate the applied force. The following embodiments are directed to different techniques and methods of detecting and measuring this displacement.

3. Exemplary Devices Having a Force Sensor

FIG. 1 depicts an exemplary device 100 that incorporates one or more force-sensing structures, as described herein. With respect to FIG. 1, the device 100 is depicted as a tablet computing device, but it should be appreciated that it may also be any of a number of other devices, including a mobile phone, portable computer, wearable device, touch screen, and the like. The device 100 may have an enclosure 102 including multiple sidewalls and a bezel 106. In other embodiments, the device 100 may be flush-mounted into a larger surface or enclosure and so the device may lack an identifiable bezel or sidewall.

As shown in FIG. 1, the electronic device 100 includes an electronic display, located beneath a cover glass 104, for conveying graphical and/or textual information to the user. The electronic display may include a liquid crystal display (LCD), organic light omitting diode (OLED), or other electronic display component. In some embodiments, the display may be omitted. For example, the cover glass may be placed over a control button or track pad that is not configured to convey graphical and/or textual information to the user. (In such a case, the cover glass may not be transparent.)

As shown in FIG. 1, the device includes multiple ports and mechanisms for electrically and mechanically coupling the device to external devices or elements. The input mechanisms, ports, and the like may vary between versions, types and styles of the electronic device 100. Accordingly, they are shown in FIG. 1 only as examples of such devices and in sample positions.

FIG. 2A depicts a cross-sectional view taken along line 1-1, shown in FIG. 1. The cross-sectional view depicts the interior of a device 100 having one type of force-sensing structure. A central portion of the enclosure 102 may enclosure electronic circuitry, mechanical structures, and other internal elements. As shown in the figure, a bezel 106 is formed around the perimeter of the device 100.

A ledge 202 may be formed along the perimeter of the bezel 106. The exact dimensions of the ledge 202 may vary between embodiments. In this embodiment, the ledge 202 includes a width configured to support the base of a force-sensing structure 200. The base of the force-sensing structure 200 may abut and attach to the top of the ledge 202 in certain embodiments. Likewise, as shown in FIG. 2A, an inner edge of the force-sensing structure 200 may be parallel and approximately aligned with an inner surface of the bezel 106. In other embodiments, the inner edge of the force-sensing structure 200 may be offset from an inner edge of the bezel 106.

As shown in FIG. 2A, a single force-sensing structure 200 may encircle the entirety of the inner cavity of the enclosure 102. That is, the force-sensing structure 200 may extend along the entirety of the perimeter of the device and along the ledge 202. Thus, it may be appreciated that the force-sensing structure 200 may be formed as a single unit or element.

FIG. 2B depicts an alternate cross-sectional view taken along line 1-1, shown in FIG. 1. As shown in FIG. 2B, the device 100 b includes an alternative force-sensing structure 200 b. In the alternative embodiment of FIG. 2B, multiple force-sensing structures 200 b may be placed at different locations along the perimeter of the bezel 106. In this example, a force-sensing structure 200 b is placed at or near each edge of the bezel 106 of the electronic device 100 b. Additionally, a force-sensing structure 200 c is placed at each of the corners of the bezel. Thus, in the example device 100 b shown in FIG. 2B, there are eight force-sensing structures (200 b, 200 c).

With regard to FIG. 2B, it should be appreciated that more or fewer force-sensing structures 200 b may be used. For example, three force-sensing structures 200 b may be used and a location of a force may be triangulated by comparing the outputs of each device. Alternately, an array of more than four force-sensing structures 200 b may be used in a device. Additionally, each of the force-sensing structures shown in FIG. 2B may represent a number of individual force-sensing structures in a linear or two-dimensional array, for example. Accordingly, the number and positioning of the various force-sensing structures 200 b depicted in FIG. 2B is merely exemplary and other variations are possible.

FIG. 3 depicts a cross-sectional view taken along 2-2 of the electronic device 100, as shown in FIG. 2A. As shown in FIG. 3, the physical relationship between the cover glass 104, bezel 106, and force-sensing structure 300 is shown in more detail, although it should be appreciated that the exact geometry, sizes, tolerances, positions and the like may vary. As shown in FIG. 3, the force-sensing structure 300 may be mounted or otherwise be positioned beneath a portion of the cover glass 104. A display element 304 may likewise be positioned beneath the cover glass 104. In some embodiments, the force-sensing structure 300 may be concealed from external view by an ink or print layer deposited on the cover glass between the cover glass 104 and the force-sensing structure 300. In other embodiments, the ink or print layer may be omitted.

In some embodiments, the display element 304 may act as an shield to electrically isolate the force-sensing structure from other components within the electronic device. Likewise, a shield may be formed on the ledge 202 and portion of the housing 102 adjacent the gap 302 in order to electrically isolate the force-sensing structure 300 from external signals, or at least reduce the impact of external noise on the force-sensing structure. The shield layers may be deposited by physical vapor deposition, as one non-limiting example. Further, any or all of the shield layers may extend into the interior of the electronic device to connect to a common or system ground. For example, the shield layer may extend from the ledge down the interior wall of the enclosure 102 to a system ground.

In certain embodiments, the ledge and/or portion of the housing may themselves act as shielding structures, rather than having any shield formed thereon. It should be appreciated that one or more of the various shield layers/structures may be electrically tied to one another in certain embodiments, although this is not necessary.

As shown in FIG. 3, the bezel 106 is adjacent to the ledge 202, which is recessed from the surface of the bezel 106 and is configured to support the force-sensing structure 300. As shown in FIG. 3, a gap 302 may exist between the interior edge of the bezel 106 and the outer edge of the cover glass 104. The gap may allow free movement of the cover glass 104 with respect to the enclosure 102.

In certain embodiments, a portion or all of the surfaces of the gap 302 may be coated with an oleophobic material. The oleophobic material may serve as a barrier against, or repel, oils, dust, dirt and other similar materials from entering the gap 302 and/or impacting the force-sensing structure 300. In this fashion the coating may serve to maintain operation of the force-sensing structure over time. Coatings other than an oleophobic coating may be used; other dust- and/or oil- and/or dirt-repellent coatings may be used in different embodiments.

As shown in FIG. 3, the force-sensing structure 300 includes multiple layers. In this example, the force-sensing structure includes an upper portion 310 and a lower portion 320 separated by a deformable middle body or compressible element 330. The upper portion 310 includes an upper body 311 which may be formed from a layer of polyimide flex material. The upper portion 310 also includes an upper capacitive plate 312 formed from a layer of copper bonded to or deposited on the upper body 311. Likewise, the lower portion 320 includes a lower body 321 which may also be formed from a layer of polyimide flex material. The lower portion 320 also includes a lower capacitive plate 322 formed from a layer of copper bonded to or deposited on the lower body 321. In this example, the polyimide flex material is approximately 0.05 millimeters thick. However, other thicknesses and other materials may be used to form the force-sensing structure 300.

As shown in FIG. 3, a capacitance (shown by the capacitor symbol) may be formed between the upper and lower capacitive plates 312, 322, which, in this example, are separated by the compressible element 330. In this example, the compressible element 300 is formed from a silicone material approximately 0.2 millimeters thick with a tolerance of plus or minus 0.09 millimeters. In other embodiments, the compressible element 300 may be formed from a different material and have a different thickness.

The force-sensing structure 300 depicted in FIG. 3 can be used to detect and measure a user-applied force. For example, a user may press down on the cover glass 104 (or on an upper surface of the electronic device 100, in embodiments lacking a display and/or cover glass) to exert a force on the device 100. The cover glass 104 may move downward in response to the force, compressing the compressible element 330 of the force-sensing structure 300. In some cases, the compressible element 330 becomes flattened by the compression resulting the in first and second capacitive plates 312, 322 moving closer together. As a result, the capacitance between the first and second capacitive plates 312, 322 may change. As previously mentioned, a change in capacitance may produce an electrical signal or change in an electrical signal, which may be detected and measured by associated circuitry and may be used to estimate the force exerted on the cover glass 104 by the user.

As shown in FIG. 3, the upper and lower capacitive plates 312, 322 may extend outward from the upper and lower bodies 311, 321, respectively. That is, at certain locations along the length of the force-sensing structure 300, a portion of the capacitive plates 312, 322 may be bare and exposed. The exposed portion of the capacitive plates may facilitate connection to a wire, conduit, or other electrical connection and allow signals to be communicated between the force-sensing structure 300 and associated electronic circuitry in order to measure capacitance changes and estimate force.

In some embodiments, a second, auxiliary structure may be formed within the device 100 or within a segment of the force-sensing structure. The auxiliary structure may also include an upper capacitive plate and a lower capacitive plate separated by a compressible element. However, the auxiliary structure may not be configured to be compressed by the cover glass 104, and instead may serve as a reference capacitance used to account for changes in environmental conditions surrounding the device. For example, the elasticity and/or compressibility of the compressible element (e.g., a silicone material) may vary due to changes in the amount of absorbed moisture. In this case, it may be advantageous to use an auxiliary structure to measure (directly or indirectly) changes in the physical properties of the compressible element to account for changes in the moisture content. In one example, the auxiliary structure may form a capacitor with the upper and lower capacitive plates separated by a compressible element. The capacitor may be connected to a second electrical circuit that monitors the capacitance between the plates of the auxiliary structure separately from any force-sensitive structure. The auxiliary structure may be positioned in a part of the device such that it does not experience any (or very little) compression when a user presses down on the cover glass but is still exposed to the same or a similar environment as the force-sensing structure. Thus, any changes in the capacitance between the plates of the auxiliary structure may be purely due to absorbed moisture and/or aging of the compressible element (e.g., a silicone material). The output signal from the auxiliary structure may be used to adjust readings from force-sensitive structure to compensate for changes in the environmental conditions that affect the physical properties of the compressible element.

FIGS. 4 and 5 depict alternative embodiments of a force-sensitive structure. Specifically, FIG. 4 depicts a force-sensitive structure 400 having an upper portion 410 including an upper body 411 attached to an upper capacitive plate 412. The force-sensitive structure 400 also includes a lower portion 420 including a lower body 421 attached to a lower capacitive plate 422. The upper and lower portions 410, 420 are separated by a compressible element 430 and form a capacitor that can be used to detect a force applied to the cover glass 104. In the example depicted in FIG. 4, the upper and lower capacitive plates 412, 422 do not extend beyond the upper and lower bodies 411, 421. In this case, electrical communication with the force-sensitive structure 400 may be facilitated by an electrical terminal or conduit located within the profile of the force-sensitive structure 400.

FIG. 5 depicts another alternative embodiment of an electronic device 100 incorporating a force-sensitive structure 500. In this embodiment, an environmental seal 550 may be positioned between the cover glass 104 and the force-sensitive structure 500 to prevent ingress of moisture, dust, dirt, and other potential environmental contaminants. The environmental seal 550 may be formed, for example, from an extruded compliant material, such as Buna rubber, Viton, EPDM, or the like. In some cases, the environmental seal 550 is formed as a bead of sealant material that cures after being applied to an element of the device 100.

Optionally, as shown in FIG. 5, the device may also include a support 552 positioned between the seal 550 and the cover glass 104 to provide a bonding surface for the environmental seal 550. In this example, the support 552 is attached to the cover glass 104 and, therefore, is movable with respect to the enclosure 102. Thus, as a force is applied to the cover glass 104, the cover glass 104, optional support 552, and seal 550 may all move downward to compress the force-sensing structure 500. Thus, in the present embodiment, the seal 550 can be used to isolate the force-sensing structure 500 from moisture and external debris while still allowing operation force-sensing structure 500. In addition to or in place of the seal 550, the device 100 may also include one or more wiping seals located between an edge of the cover glass 104 and a portion of the enclosure 102. Furthermore, a baffle seal or membrane may be installed between the cover glass 104 and a portion of the enclosure 102, the baffle seal configured to prevent contaminates from entering the internal portion of the device 100.

In some embodiments, the environmental seal 550 is compliant and in other embodiments, the environmental seal 550 is not compliant and may be rigid. A rigid seal may be advantageous by transmitting force to the force-sensing structure 500 directly, while a compliant or flexible seal may compress somewhat before transmitting any force. Either type of seal may be used, although the output of the force-sensitive structure 500 may be affected by compression of a flexible seal.

FIG. 6 depicts another alternative embodiment of a device having a capacitive force sensor. As shown in FIG. 6, a touch device case 605 (e.g., housing) can be shaped and positioned to hold a cover glass element 610. For example, the touch device case 605 can include a rectilinear frame, such as having a shape of a picture frame, with the cover glass element 610 having the shape of a picture cover (as would occur if a picture were placed below the cover glass element 610). The touch device case 605 can include a backing (not shown) or a midframe element (not shown), which can stabilize the touch device case 605 against bending, warping, or other physical distortion. The touch device case 605 can also define a space in which circuitry for the touch device (as described herein) can be positioned. This has the effect that the circuitry for the touch device can be protected against foreign contaminants or unwanted touching, and against bending or warping, or other electrical or physical effects that might possibly cause circuitry errors or other problems for the touch device.

As shown in FIG. 6, the touch device case 605 can include an outer edge 615, such as can be defined by an outer lip or a protrusion upward from a baseline of the touch device case 605, and which can be positioned to prevent excess slippage or other movement of the cover glass element 610 in either an X or Y direction. In this context, a Z direction generally indicates a direction substantially normal (likely to be at a 90 degree angle, but this is not required) to a plane of the cover glass element 610 and a top surface of the touch device, while the X and Y directions generally indicate directions substantially within the same plane of the cover glass element 610 (likely to be at 90 degree angles with respect to each other, but this is not required).

As shown in FIG. 6, the cover glass element 610 and the outer edge 615 define a cover glass gap 620 between them, with the effect that the cover glass element 610 does not bump or rub against the touch device case 605. In one embodiment, the touch device can include an optional elastomer 625, or other substance, positioned between the cover glass element 610 and the outer edge 615. This can have the effect of providing shock absorption in the event of a sudden acceleration of the cover glass element 610 in the direction of the outer edge 615, such as in the event the touch device is dropped, hit, kicked, or otherwise catastrophically moved. For example, the elastomer 625 can be disposed around the edges of the cover glass element 610, with the effect of forming an O-ring shape or similar shape. The elastomer 625 can also have the effect of preventing, or at least militating against, foreign object damage that might be caused by dust or other objects slipping between the cover glass element 610 and the outer edge 615.

As shown in FIG. 6, the touch device case 605 includes a cover glass shelf 630, such as can be defined by an inner lip or internal protrusion inward from the outer edge 615 of the touch device case 605, and which can be positioned to support the cover glass element 610. For example, the cover glass element 610 can rest on the cover glass shelf 630, which can prevent the cover glass element 610 from slipping down into the circuitry for the touch device. In alternative embodiments, the touch device case 605 can include a midframe (not shown), such as can be defined by an internal support element positioned to support the cover glass element 610. For example, the midframe can include a relatively solid (absent optional holes) element positioned to support at least some of the circuitry for the touch device.

As shown in FIG. 6, the device includes a force-sensing structure 600. In this example, the force-sensing structure 600 includes a first upper portion comprising a first pressure sensitive adhesive (PSA) layer 635, having a thickness of about 100 microns and a first flex circuit 640. The first flex circuit 640 includes a set of drive/sense lines configured to conduct electric signals and/or act a capacitive plate. The force-sensing structure 600 also includes a lower portion comprising a second PSA layer 645, such as also having a thickness of about 100 microns, and a second flex circuit 650 also having conductive drive/sense lines for conducting signals and acting as a capacitive plate. The first flex circuit 640 and the second flex circuit 650 are configured to operate in response to control by the drive/sense lines and can form a capacitive sensor. As explained above with respect to previous embodiments, changes in the capacitance between the upper and lower portions of the force-sensing structure 600 may be related to an amount of deflection or change in distance between the first flex circuit 640 and the second flex circuit 650. (In other embodiments, one or more strain gauges can be used instead of a capacitive sensor.) In one example, if the cover glass element 610 is tilted (such as by pressure or other applied force), the first flex circuit 640 and the second flex circuit 650 can become closer or become farther away, depending on location with respect to the axis and location of tilt. As further described herein, the first flex circuit 640 and the second flex circuit 650 can be replicated in several locations on the touch device case 605.

The force-sensing structure 600 is typically operatively connected to a force-sensing circuit configured to detect and measure changes in capacitance. By measuring changes in capacitance, the force-sensing circuit can be used to estimate relative displacement of one or more force-sensing structures which, in turn can be used to determine an axis and location of tilt of the cover glass element 610. Furthermore, the changes in capacitance can be used to estimate a force applied to the cover glass element 610. In some embodiments, the force-sensing circuit includes or is coupled to a processor.

In one embodiment, a region between the first flex circuit 640 and the second flex circuit 650 can define a substantially empty space (that is, filled with air). In alternative embodiments, the region between the first flex circuit 640 and the second flex circuit 650 can include a compressible layer 655. For a first example, the space between the first and second flex circuits 640, 650 can include a set of spring elements interspersed within the space. In this case, the first flex circuit 640 and the second flex circuit 650 are held apart by spring forces and do not generally touch. For a second example, the compressible layer 655 can include a microstructure constructed at least in part from silicone, such as a set of silicone pyramids or a set of silicone springs, also with the effect that the first flex circuit 640 and the second flex circuit 650 are held apart by a spring force and do not generally touch.

As described generally above, the cover glass element 610 may include a transparent touch sensor that is configured to detect the location of one or more touches. As mentioned previously, the transparent touch sensor may be formed from one or more arrays of transparent conductive lines coupled to touch sensor circuitry. Types of transparent touch sensors that may be integrated into the cover glass element 610, include, without limitation, mutual capacitive sensors, self-capacitive touch sensors, and resistive touch sensors.

In one embodiment, an area of the cover glass element 610 above the first flex circuit 640 and the second flex circuit 650 can be covered with an ink mask 660. In one embodiment, the ink mask 660 is disposed below the cover glass element 610 and above the first flex circuit 640. This has the effect that a user of the touch device does not generally see either the first flex circuit 640 or the second flex circuit 650, or any of the elements coupling them to the touch device case 605, the cover glass element 610, or any circuits for touch device (not shown). For example, the touch device can include a surface 665, which can include a surface of the cover glass element 610 in places where the ink mask 660 is absent, and can include a surface of the ink mask where the ink mask 660 is present. As described above, a Z direction 670 can indicate a direction substantially normal to the surface 665 of the touch device.

In one embodiment, the interaction between the cover glass element 610 and the outer edge 615 may result in a set of forces at the outer edge of the cover glass element 610. In some embodiments, a force-sensing structure 600 (or alternatively a strain gauge) is placed at two or more edges of the cover glass element 610. Each of the two or more force-sensing structures may be operatively coupled to force-sensing circuitry in the touch device and can be used to detect and measure these forces. Additionally, by estimating the relative displacement in each of the two or more force-sensing structures, the circuit can be used to determine a normal vector to the cover glass element 610 that represents a location of applied force (that is, a location of the normal vector) as well as an amount applied force (that is, a magnitude of the normal vector).

In one embodiment, the normal vector can be determined in response to an amount of tilt of the cover glass element or an amount of pressure at a X and the Y location. For example, a set of displacements can be measured using two or more force-sensing structures located at one or more edges on the perimeter of the cover glass element. In one embodiment, the displacements are proportional or can be correlated to one or more applied forces. A total force Fz can be determined in response to the individual forces at the edges of the cover glass element, and a centroid location (x0, y0) can be determined based on a correlation between the individual forces. Thus, using two or more force-sensing structures, a total force Fz and central location (x0, y0) can be computed that correlates to the actual force exerted on the cover glass element. Additionally, signals generated by multiple force-sensing structures can be coupled with the output of a touch sensor (potentially integrated into the cover glass elements) to resolve both the location a magnitude (applied force) for multiple finger touches on a cover glass element.

FIG. 7 depicts another exemplary embodiment of a device having a capacitive force sensor. The device may include a touch-sensitive region 710, which may (or may not) coincide with a display region such as an LED, LCD or OLED display. In this example, the touch-sensitive region 710 is formed from a transparent touch sensor integrated with the cover glass element 610.

FIG. 7 depicts, the touch device as viewed from above and includes the touch device case 605, the cover glass element 610, and the outer edge 615. The touch device also includes a home button 705, and a touch-sensitive region 710 (in which the touch device can determine a location of one or more touches using, for example, a capacitive touch sensor). The home button 705 may be partially or fully within the touch-sensitive region 710, or may be located outside the touch-sensitive region 710.

In one embodiment, the shape of the touch device can be indicated by a pair of centerlines 715, such as an X direction centerline 715 x and a Y direction centerline 715 y. The touch device can include, along one or more edges, such as bordering the touch-sensitive region 710, a set of force sensors 700. The force sensors 700 may be formed from one or more capacitive force sensors similar to those as described with respect to FIGS. 3-6. Alternatively, the force sensors 700 may include other devices capable of sensing applied force, such as a strain gauge.

As shown in FIG. 7, a device may include a plurality of force sensors 700 located along one or more edges of the perimeter of the touch-sensitive region 710. Each force sensor 700 includes at least two capacitive plates separated by a compressible intermediate layer. In one embodiment, the set of force sensors 700 can be disposed substantially outside a transparent portion of the touch-sensitive region 710. For example, the force sensors 700 may be located under an ink mask 660 (such as similar to or like that described with reference to the FIG. 6). In such cases, the force sensors 700 can be positioned with a gauge spacing 725 between pairs of the force sensors 700, and with an edge spacing 730 between individual ones of the force sensors 700 and an edge the touch device. In alternative embodiments, the force sensors 700 may be positioned beneath a display stack or located in another position with respect to the touch-sensitive region 710. The force sensors 700 may be evenly spaced from one another, spaced at uneven intervals, at repeating intervals, or as necessary. Likewise, the force sensors 700 may be positioned along all sides of the touch-sensitive region 710, at corners of the device, along less than all sides of the touch-sensitive region 710, or along a single edge of the touch-sensitive region 710. Accordingly, the sensor distribution shown in FIG. 7 is meant to be a sample, partial distribution and not limiting.

In one embodiment, each force sensor 700 is coupled to force-sensing circuitry that is configured to measure an amount of capacitance between a first flex circuit and a second flex circuit, which may be correlated to estimate a distance between the first flex circuit and the second flex circuit. The relative position of the first and second flex circuits may be similar to the configuration depicted in FIG. 6, discussed above. Similar to embodiments described above, an amount of capacitance between the first sensing element defined on the first flex circuit and the second sensing element defined on the second flex circuit can be detected and measured using force detection circuitry, which may include a processor. In such cases, the amount of applied force can be correlated to a relative change in distance between the first flex circuit and the second flex circuit, relative to a rest position when there is no force applied to the cover glass element 610. It should be appreciated that each force sensor 700 may be formed from first and second flex circuits, or may be a separate element.

In an alternative embodiment, each force sensor 700 is coupled to force-sensing circuitry that is configured to measure an amount of resistance between the first flex circuit and the second flex circuit. For example, the first and second flex circuits may be coupled by resistive layer. By measuring the resistance or change in resistance, the force-sensing circuitry can be used to determine a distance between the first flex circuit and the second flex circuit. For example, an amount of resistance between the first flex circuit and the second flex circuit can be correlated to a distance between the first flex circuit and the second flex circuit. This may occur when, for example the compressible, resistive layer is formed from a material that has a variable resistivity dependent on its thickness or an amount of compression. In one such case, the compressible, resistive layer includes a microstructure that has a resistance that increases like a spring force, similar to a strain gauge. The force-sensing circuitry may estimate the distance between the flex circuits by measuring the resistance or changes to the resistance in the compressible, resistive layer.

With reference to FIG. 7, the force sensors 700 can be operatively coupled to force-sensing circuitry (including a processor) that is configured to determine a set of distances (at distinct locations along the edge of the cover glass element 110) corresponding to the set of force sensors 700. That is, the force-sensing circuitry can estimate the distance between the first flex circuit and the second flex circuit based on the measured capacitance at each force sensor. In one embodiment, the displacements at each sensor 700 correlate to applied forces at the locations of those force sensors 700. Similar to the technique described above with respect to FIG. 6, a total force Fz can be determined based on an estimate of the individual forces, and a centroid location (x0, y0) can be determined based on a weighting of the estimate of the individual forces. In one embodiment, the total force Fz and the centroid location (x0, y0) is calibrated such that a set of computed forces and moments in response to the values of the total force Fz and the centroid location (x0, y0) best matches the observed values for displacements and forces at each of the set of force sensors 700. Thus, using multiple force sensors, a total force Fz and central location (x0, y0) can be computed that correlates to the actual force exerted on the device. Additionally, signals generated by multiple force sensors can be coupled with the output of a touch sensor (potentially integrated into the cover glass elements) to resolve both the locations and magnitudes (due to applied forces) for multiple finger touches on the device.

FIG. 8 depicts another exemplary embodiment of a device having a capacitive force sensor. In particular, the device depicted in FIG. 8 includes a cover glass element that is deformable.

As shown in FIG. 8, a cover glass element 805 can be coupled to a frame element 810, which can be coupled to a touch device frame 815. In one embodiment, there is a spatial separation between the cover glass element 805 and the frame element 810. For a first example, the cover glass element 805 can have a thickness of about 0.90 mm, although this particular thickness is merely exemplary and is not required. For a second example, the frame element 810 can include an elastomer, a plastic, or include construction from other substances. The cover glass element 805 can also be positioned above a display stack 820, such as a display stack from a touch device and adapted to provide a graphical or text display.

In one embodiment, the display stack 820 can be positioned above a reflector sheet 825 including an electrode pattern, such as can be used for drive and sense lines in a rectilinear capacitive array or individual sensor structures in an array. The reflector sheet 825 can be positioned above an air gap 830, such as can be used for capacitance between the reflector sheet 825 and another element. For example, the air gap 830 can have a thickness of about 0.10 mm, although this particular thickness is merely exemplary and is not required.

In one embodiment, the air gap 830 can be positioned above a circuit 835 having capacitive traces or elements, which may include a set of drive and sense traces/elements or be formed from an array of individual sensing traces/elements. For example, the circuit 835 can have a thickness of about 0.10 mm, although this particular thickness is merely exemplary and is not required.

In one embodiment, the circuit 835 can be positioned above a pressure sensitive adhesive (PSA) element 840. For example, the PSA element 840 can have a thickness of about 0.03 mm, although this particular thickness is merely exemplary and is not required. Further, a primer may be used between PSA and the housing to affix the structure to the housing. The structure may be optically aligned with the housing prior to bonding.

In one embodiment, the PSA element 840 can be positioned above a midplate element 845. For a first example, the midplate element 845 can have a thickness of about 0.25 mm, although this particular thickness is merely exemplary and is not required. For a second example, the midplate element 845 can be supportive of the elements coupled thereto and below the air gap 830.

In one embodiment, the cover glass element 805, the display stack 820, and related elements can be relatively deformable. This can have the effect that applied force to the surface of the touch device can cause a change in distance between elements near the air gap 830, and a change in measured capacitance by circuits positioned near the air gap 830. For example, a set of drive and sense lines, or an array of individual sensing elements, could be positioned in the reflector sheet 825 or in the circuit 835, can measure a capacitance across the air gap 830.

In such cases, the capacitance across the air gap 830 would be subject to change in response to deformation of the cover glass element 805, the display stack 820, and related elements. This would have the effect that elements positioned near the air gap 830 would be able to measure the change in capacitance, and would be able to determine an amount or magnitude of an applied force in response thereto.

In some embodiments, multiple force sensors may be formed over the area of the cover glass element 805. In one embodiment, the set of force sensors can be positioned in a rectilinear array, such as an array in which each one of the force sensors is positioned at an [X, Y] location over the area of the cover glass element 805. For example, each one of the force sensors can include a capacitive force sensor exhibiting mutual capacitance between drive and sensor elements, or exhibiting self-capacitance. In another example, each one of the sensors can include a resistive strain gauge exhibiting a change in resistance in response to applied force, such as a resistive strain gauge as described with respect to FIG. 6, above.

In one embodiment, the applied force can affect each force sensor that is substantially near the applied force. The applied force affects each such force sensor differently depending on an amount of the applied force and a distance between the [X, Y] location of the applied force and the [X, Y] location of the affected force sensor. This has the effect that a processor or other circuit in the touch device can determine a mapping of applied force, and in response thereto, a set of [X, Y] locations and a Z displacement of the cover glass element 805. For example, particular Z displacement of points along the edges of the cover glass element 805 (or within a touch-sensitive region) can be used to determine the [X, Y] location of the applied force. In one embodiment, the cover glass element 805 may be approximately 700 microns thick, although this thickness may vary between embodiments.

In one embodiment, the same or similar information can be used to determine the [X, Y] location and Z displacement of more than one such applied force. In such cases where multiple forces are applied, a processor or other circuit in the touch device can determine a centroid of applied force, from which the touch device can determine one or more individual forces. For example, from this information, a processor or other circuit can determine one or more [X, Y] locations where force is being applied, and an amount or magnitude of force being applied at each such location.

In one embodiment, the interaction between the cover glass element 805 and the air gap 830 defines a set of forces at each location of applied force. A processor or other circuit in the touch device can measure these forces, such as using one or more capacitive sensing elements (as described herein) or using one or more strain gauges, distributed at locations throughout cover glass element 805. In response to those forces, the circuit can determine a set of normal vectors to the cover glass element 805 representing one or more locations of applied force and one or more amounts or magnitudes of the applied force.

In one embodiment, the locations of applied force can be determined in response to the distribution of sensed applied force at each location on the cover glass element 805, as described above, at each of the X and the Y locations, thus assigning each such location a Z amount of applied force. For a first example, a total centroid of applied force can be determined in response to the distribution of sensed applied force. The processor or other circuit can then locate each individual likely applied force, identify its amount of force, and subtract out that identified force from the sensed applied force at each location. This can have the effect of providing the processor or other circuit with a way to identify each applied force individually, until all such individual applied forces have been found.

In one embodiment, an amount or magnitude of force can be determined at each of a set of distinct locations at which a distinct force sensor is disposed below the cover glass element 805. For example, in one embodiment, the force sensors can be disposed in a grid below the cover glass element 805. Having the amount of force at each such location, a weighted centroid of that set of force amounts can be computed using a weighted sum of the locations at which each applied force is measured. Having determined such a centroid, the processor can determine a nearest local maximum force, either in response to the nearest maximum force sensor, or in response to a touch location sensor, or both. Having determined a nearest local maximum force, the processor can subtract that force and its expected effect on each force sensor, and repeat the process until each individual applied force is determined. In alternative embodiments, other and further techniques could be used in addition or instead.

4. Force-Sensitive Device System

FIG. 9 depicts an exemplary communication between a touch I/O device and a computing system. In this example, the touch I/O device 901 includes one or more sensors for detecting a touch by an operator or user. The touch device 901 transmits electronic signals from the one or more sensors to a computing system 903 over a communication channel 902. An example computing system 903 is described below with respect to FIG. 10 and includes one or more computer processors and computer-readable memory for storing computer-executable instructions. The touch I/O device, communication channel 902 and computing system 903 may all be integrated together as a part of the same touch device.

As shown in FIG. 9, embodiments may include touch I/O device 901 that can receive touch input and force input (such as possibly including touch locations and applied force at those locations) for interacting with computing system 903 via wired or wireless communication channel 902. Touch I/O device 901 may be used to provide user input to computing system 903 in lieu of or in combination with other input devices such as a keyboard, mouse, or possibly other devices. In alternative embodiments, touch I/O device 901 may be used in conjunction with other input devices, such as in addition to or in lieu of a mouse, trackpad, or possibly another pointing device. One or more touch I/O devices 901 may be used for providing user input to computing system 903. Touch I/O device 901 may be an integral part of computing system 903 (e.g., touch screen on a laptop) or may be separate from computing system 903.

Touch I/O device 901 may include a touch sensitive and/or force sensitive panel which is wholly or partially transparent, semitransparent, non-transparent, opaque or any combination thereof. Touch I/O device 901 may be embodied as a touch screen, touch pad, a touch screen functioning as a touch pad (e.g., a touch screen replacing the touchpad of a laptop), a touch screen or touchpad combined or incorporated with any other input device (e.g., a touch screen or touchpad disposed on a keyboard, disposed on a trackpad or other pointing device), any multi-dimensional object having a touch sensitive surface for receiving touch input, or another type of input device or input/output device.

In one example, touch I/O device 901 is a touch screen that may include a transparent and/or semitransparent touch-sensitive and force-sensitive panel at least partially or wholly positioned over at least a portion of a display. (Although, the touch sensitive and force sensitive panel is described as at least partially or wholly positioned over at least a portion of a display, in alternative embodiments, at least a portion of circuitry or other elements used in embodiments of the touch sensitive and force sensitive panel may be at least positioned partially or wholly positioned under at least a portion of a display, interleaved with circuits used with at least a portion of a display, or otherwise.) According to this embodiment, touch I/O device 901 functions to display graphical data transmitted from computing system 903 (and/or another source) and also functions to receive user input. In other embodiments, touch I/O device 901 may be embodied as an integrated touch screen where touch sensitive and force sensitive components/devices are integral with display components/devices. In still other embodiments a touch screen may be used as a supplemental or additional display screen for displaying supplemental or the same graphical data as a primary display and to receive touch input, including possibly touch locations and applied force at those locations.

Touch I/O device 901 may be configured to detect the location of one or more touches or near touches on device 901, and where applicable, force of those touches, based on capacitive, resistive, optical, acoustic, inductive, mechanical, chemical, or electromagnetic measurements, in lieu of or in combination or conjunction with any phenomena that can be measured with respect to the occurrences of the one or more touches or near touches, and where applicable, force of those touches, in proximity to the touch I/O device 901. Software, hardware, firmware or any combination thereof may be used to process the measurements of the detected touches, and where applicable, force of those touches, to identify and track one or more gestures. A gesture may correspond to stationary or non-stationary, single or multiple, touches or near touches, and where applicable, force of those touches, on touch I/O device 901. A gesture may be performed by moving one or more fingers or other objects in a particular manner on touch I/O device 901 such as tapping, pressing, rocking, scrubbing, twisting, changing orientation, pressing with varying pressure and the like at essentially the same time, contiguously, consecutively, or otherwise. A gesture may be characterized by, but is not limited to a pinching, sliding, swiping, rotating, flexing, dragging, tapping, pushing and/or releasing, or other motion between or with any other finger or fingers, or any other portion of the body or other object. A single gesture may be performed with one or more hands, or any other portion of the body or other object by one or more users, or any combination thereof.

Computing system 903 may drive a display with graphical data to display a graphical user interface (GUI). The GUI may be configured to receive touch input, and where applicable, force of that touch input, via touch I/O device 901. Embodied as a touch screen, touch I/O device 901 may display the GUI. Alternatively, the GUI may be displayed on a display separate from touch I/O device 901. The GUI may include graphical elements displayed at particular locations within the interface. Graphical elements may include but are not limited to a variety of displayed virtual input devices including virtual scroll wheels, a virtual keyboard, virtual knobs or dials, virtual buttons, virtual levers, any virtual UI, and the like. A user may perform gestures at one or more particular locations on touch I/O device 901 which may be associated with the graphical elements of the GUI. In other embodiments, the user may perform gestures at one or more locations that are independent of the locations of graphical elements of the GUI. Gestures performed on touch I/O device 901 may directly or indirectly manipulate, control, modify, move, actuate, initiate, or generally affect graphical elements such as cursors, icons, media files, lists, text, all or portions of images, or the like within the GUI. For instance, in the case of a touch screen, a user may directly interact with a graphical element by performing a gesture over the graphical element on the touch screen. Alternatively, a touch pad generally provides indirect interaction. Gestures may also affect non-displayed GUI elements (e.g., causing user interfaces to appear) or may affect other actions within computing system 903 (e.g., affect a state or mode of a GUI, application, or operating system). Gestures may or may not be performed on touch I/O device 901 in conjunction with a displayed cursor. For instance, in the case in which gestures are performed on a touchpad, a cursor (or pointer) may be displayed on a display screen or touch screen and the cursor may be controlled via touch input, and where applicable, force of that touch input, on the touchpad to interact with graphical objects on the display screen. In other embodiments in which gestures are performed directly on a touch screen, a user may interact directly with objects on the touch screen, with or without a cursor or pointer being displayed on the touch screen.

Feedback may be provided to the user via communication channel 902 in response to or based on the touch or near touches, and where applicable, force of those touches, on touch I/O device 901. Feedback may be transmitted optically, mechanically, electrically, olfactory, acoustically, haptically, or the like or any combination thereof and in a variable or non-variable manner.

As previously mentioned, the touch I/O device, communication channel 902, and the computing system 903 may all be integrated into a touch device or other system. The touch device or system may be a portable or non-portable device, including, but not limited to, a communication device (e.g., mobile phone, smart phone), a multi-media device (e.g., MP3 player, TV, radio), a portable or handheld computer (e.g., tablet, netbook, laptop), a desktop computer, an all-in-one desktop, a peripheral device, or any other (portable or non-portable) system or device adaptable to the inclusion of system architecture depicted in FIG. 10, including combinations of two or more of these types of devices.

FIG. 10 depicts a block diagram of one embodiment of system 1000 that generally includes one or more computer-readable media 1001, processing system 1004, Input/Output (I/O) subsystem 1006, electromagnetic frequency circuitry, such as possibly radio frequency (RF) or other frequency circuitry 1008 and audio circuitry 1010. These components may be coupled by one or more communication buses or signal lines 1003. Each such bus or signal line may be denoted in the form 1003-X, where X can be a unique number. The bus or signal line may carry data of the appropriate type between components; each bus or signal line may differ from other buses/lines, but may perform generally similar operations.

It should be apparent that the architecture shown in FIG. 10 is only one example architecture of system 1000, and that system 1000 could have more or fewer components than shown, or a different configuration of components. The various components shown in FIG. 10 can be implemented in hardware, software, firmware or any combination thereof, including one or more signal processing and/or application specific integrated circuits.

Shown in FIG. 10, RF circuitry 1008 is used to send and receive information over a wireless link or network to one or more other devices and includes well-known circuitry for performing this function. RF circuitry 1008 and audio circuitry 1010 are coupled to processing system 1004 via peripherals interface 1016. Interface 1016 includes various known components for establishing and maintaining communication between peripherals and processing system 1004. Audio circuitry 1010 is coupled to audio speaker 1050 and microphone 1052 and includes known circuitry for processing voice signals received from interface 1016 to enable a user to communicate in real-time with other users. In some embodiments, audio circuitry 1010 includes a headphone jack (not shown).

Peripherals interface 1016 couples the input and output peripherals of the system to processor 1018 and computer-readable medium 1001. One or more processors 1018 communicate with one or more computer-readable media 1001 via controller 1020. Computer-readable medium 1001 can be any device or medium that can store code and/or data for use by one or more processors 1018. Medium 1001 can include a memory hierarchy, including but not limited to cache, main memory and secondary memory. The memory hierarchy can be implemented using any combination of RAM (e.g., SRAM, DRAM, DDRAM), ROM, FLASH, magnetic and/or optical storage devices, such as disk drives, magnetic tape, CDs (compact disks) and DVDs (digital video discs). Medium 1001 may also include a transmission medium for carrying information-bearing signals indicative of computer instructions or data (with or without a carrier wave upon which the signals are modulated). For example, the transmission medium may include a communications network, including but not limited to the Internet (also referred to as the World Wide Web), intranet(s), Local Area Networks (LANs), Wide Local Area Networks (WLANs), Storage Area Networks (SANs), Metropolitan Area Networks (MAN) and the like.

One or more processors 1018 run various software components stored on medium 1001 to perform various functions for system 1000. In some embodiments, the software components include operating system 1022, communication module (or set of instructions) 1024, touch and applied force processing module (or set of instructions) 1026, graphics module (or set of instructions) 1028, and one or more applications (or set of instructions) 1030. Each of these modules and above noted applications correspond to a set of instructions for performing one or more functions described above and the methods described in this application (e.g., the computer-implemented methods and other information processing methods described herein). These modules (i.e., sets of instructions) need not be implemented as separate software programs, procedures or modules, and thus various subsets of these modules may be combined or otherwise rearranged in various embodiments. In some embodiments, medium 1001 may store a subset of the modules and data structures identified above. Furthermore, medium 1001 may store additional modules and data structures not described above.

Operating system 1022 includes various procedures, sets of instructions, software components and/or drivers for controlling and managing general system tasks (e.g., memory management, storage device control, power management, etc.) and facilitates communication between various hardware and software components.

Communication module 1024 facilitates communication with other devices over one or more external ports 1036 or via RF circuitry 1008 and includes various software components for handling data received from RF circuitry 1008 and/or external port 1036.

Graphics module 1028 includes various known software components for rendering, animating and displaying graphical objects on a display surface. In embodiments in which touch I/O device 1012 is a touch sensitive and force sensitive display (e.g., touch screen), graphics module 1028 includes components for rendering, displaying, and animating objects on the touch sensitive and force sensitive display.

One or more applications 1030 can include any applications installed on system 1000, including without limitation, a browser, address book, contact list, email, instant messaging, word processing, keyboard emulation, widgets, JAVA-enabled applications, encryption, digital rights management, voice recognition, voice replication, location determination capability (such as that provided by the global positioning system, also sometimes referred to herein as “GPS”), a music player, and otherwise.

Touch processing module 1026 includes various software components for performing various tasks associated with touch I/O device 1012 including but not limited to receiving and processing touch input and applied force input received from I/O device 1012 via touch I/O device controller 1032. In some cases, the touch processing module 1026 includes computer instructions for operating the force sensor 1060. For example, the touch processing module 1026 may include instructions for performing one or more operations described below with respect to processes 1100 and 1150 of FIGS. 11A-B. In some cases, the touch processing module 1026 includes parameters or settings that may be implemented in the operation of the force sensor 1060.

I/O subsystem 1006 is coupled to touch I/O device 1012 and one or more other I/O devices 1014 for controlling or performing various functions. Touch I/O device 1012 communicates with processing system 1004 via touch I/O device controller 1032, which includes various components for processing user touch input and applied force input (e.g., scanning hardware). One or more other input controllers 1034 receives/sends electrical signals from/to other I/O devices 1014. Other I/O devices 1014 may include physical buttons, dials, slider switches, sticks, keyboards, touch pads, additional display screens, or any combination thereof.

If embodied as a touch screen, touch I/O device 1012 displays visual output to the user in a GUI. The visual output may include text, graphics, video, and any combination thereof. Some or all of the visual output may correspond to user-interface objects. Touch I/O device 1012 forms a touch-sensitive and force-sensitive surface that accepts touch input and applied force input from the user. Touch I/O device 1012 and touch screen controller 1032 (along with any associated modules and/or sets of instructions in medium 1001) detects and tracks touches or near touches, and where applicable, force of those touches (and any movement or release of the touch, and any change in the force of the touch) on touch I/O device 1012 and converts the detected touch input and applied force input into interaction with graphical objects, such as one or more user-interface objects. In the case in which device 1012 is embodied as a touch screen, the user can directly interact with graphical objects that are displayed on the touch screen. Alternatively, in the case in which device 1012 is embodied as a touch device other than a touch screen (e.g., a touch pad or trackpad), the user may indirectly interact with graphical objects that are displayed on a separate display screen embodied as another I/O device 1014.

In embodiments in which touch I/O device 1012 is a touch screen, the touch screen may use LCD (liquid crystal display) technology, LPD (light emitting polymer display) technology, OLED (organic LED), or OEL (organic electro luminescence), although other display technologies may be used in other embodiments.

Feedback may be provided by touch I/O device 2012 based on the user's touch, and applied force, input as well as a state or states of what is being displayed and/or of the computing system. Feedback may be transmitted optically (e.g., light signal or displayed image), mechanically (e.g., haptic feedback, touch feedback, force feedback, or the like), electrically (e.g., electrical stimulation), olfactory, acoustically (e.g., beep or the like), or the like or any combination thereof and in a variable or non-variable manner.

System 1000 also includes power system 1044 for powering the various hardware components and may include a power management system, one or more power sources, a recharging system, a power failure detection circuit, a power converter or inverter, a power status indicator and any other components typically associated with the generation, management and distribution of power in portable devices.

In some embodiments, peripherals interface 1016, one or more processors 1018, and memory controller 1020 may be implemented on a single chip, such as processing system 1004. In some other embodiments, they may be implemented on separate chips.

In one embodiment, an example system includes a force sensor 1060 integrated with the touch I/O device 2012. The force sensor 1060 may include one or more of the force-sensitive structures described above with respect to any one of the example embodiments. Generally, the force sensor 1060 is configured to generate an electronic signal or response that can be interpreted or processed as a magnitude of force of a touch on touch O/I device 1012. In some cases, the force sensor 1060 transmits electronic signals directly to the touch I/O device via signal line 1003-10. The signals may be relayed to the force sensor controller 1061 in the I/O subsystem 1006. In some cases, the force sensor 1060 transmits signals directly to the force sensor controller 1061 via signal line 1003-11 without passing through the touch I/O device 1012.

The force sensor controller 1061 either alone or in combination with one or more of the processors (e.g., processor 1018 or secure processor 1040) may serve as the force sensing circuitry for the force sensor 1060. In particular, the force sensor controller 1061 can be coupled to a processor or other computing device, such as the processor 1018 or the secure processor 1040. In one example, the force sensor controller 1061 is configured to calculate and estimated force based on electronic signals generated by the force sensor 1060. Data regarding estimated force may be transmitted to the processor 1018 or secure processor 1040 for use with other aspects of the system 1000, such as the touch processing module 1026. In one example, the force sensor controller 1061 performs signal processing on the electronic signal that is produced by the force sensor 1060, including, for example, analog to digital conversion, filtering, and sampling operations. In some cases, other processors in the system 1000 (e.g., processor 1018 or secure processor 1040) that calculate an estimated force based on the processed signal. As a result, the system 1000 can utilize signals or data produced by the force sensor controller 1061, which can be measured, calculated, computed, or otherwise manipulated. In one embodiment, the output of the force sensor 1060 is used by one or more processors or other computing devices, coupled to or accessible to the force sense controller 1061 or the touch I/O device, such as the processor 1018, the secure processor 1040, or otherwise. Additionally, output from the force sensor 1060 can be used by one or more analog circuits or other specialized circuits, coupled to or accessible to the force sensor controller 1061 or the touch I/O device 1012.

After reading this application, those skilled in the art would recognize that techniques for obtaining information with respect to applied force and contact on a touch I/O device, and using that associated information to determine the magnitude and locations of applied force and contact on a touch I/O device, is responsive to, and transformative of, real-world data such as attenuated reflection and capacitive sensor data received from applied force or contact by a user's finger, and provides a useful and tangible result in the service of detecting and using applied force and contact with a touch I/O device. Moreover, after reading this application, those skilled in the art would recognize that processing of applied force and contact sensor information by a computing device includes substantial computer control and programming, involves substantial records of applied force and contact sensor information, and involves interaction with applied force and contact sensor hardware and optionally a user interface for use of applied force and contact sensor information.

Certain aspects of the embodiments described in the present disclosure may be provided as a computer program product, or software, that may include, for example, a computer-readable storage medium or a non-transitory machine-readable medium having stored thereon instructions, which may be used to program a computer system (or other electronic devices) to perform a process according to the present disclosure. A non-transitory machine-readable medium includes any mechanism for storing information in a form (e.g., software, processing application) readable by a machine (e.g., a computer). The non-transitory machine-readable medium may take the form of, but is not limited to, a magnetic storage medium (e.g., floppy diskette, video cassette, and so on); optical storage medium (e.g., CD-ROM); magneto-optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM and EEPROM); flash memory; and so on.

While the present disclosure has been described with reference to various embodiments, it will be understood that these embodiments are illustrative and that the scope of the disclosure is not limited to them. Many variations, modifications, additions, and improvements are possible. More generally, embodiments in accordance with the present disclosure have been described in the context of particular embodiments. Functionality may be separated or combined in procedures differently in various embodiments of the disclosure or described with different terminology. These and other variations, modifications, additions, and improvements may fall within the scope of the disclosure as defined in the claims that follow.

5. Methods of Operation

FIG. 11A depicts an exemplary process for operating a device having a force sensor. The process may be applied using the force sensors described above with respect to FIGS. 2A, 2B, 3-8, discussed above.

FIG. 11A depicts an exemplary flow chart for a process 1100 that includes flow points and operational steps or functions. Although these flow points and operations are shown in a particular order, in the context of a more generalized technique, there is no particular requirement that the order of the operations must be followed as shown. For example, the flow points and operations could be performed in a different order, concurrently, in parallel, or otherwise. Similarly, although these flow points and operations are shown performed by a general purpose processor in a device, in the context of a more generalized approach, there is no particular requirement for any such limitation. For example, one or more such operations could be performed by a special purpose processor, by another circuit, or be offloaded to other processors or other circuits in other devices, such as by offloading those functions to nearby devices using wireless technology or by offloading those functions to cloud computing functions. In some cases, prior to performing the operations of process 1100, the electronic device has been turned on and the operating system has been loaded and is running. Also, the relevant hardware including, for example, touch screen sensors, display devices, and force sensor devices may have been powered and may have been initialized.

At operation 1105, a force is applied to a location [X, Y] on the cover glass of the device. The force may be applied using either a finger or other pointing devices, such as a stylus or pen. In some cases, multiple touches may be applied to the cover glass of the device. For example, a multi-touch gesture or command may be input on the cover glass resulting in a net applied force.

At operation 1110, an electrical signal is detected and measured in response to the applied force. In one example, force-sensing circuit (which may include a processor) in the device measures a value from one or more force sensors in response to the applied force. In one embodiment, as described above with respect to FIGS. 2A, 2B, and 3-5, a force-sensing circuit detects a change in the capacitance at one or more force-sensing structures. The change in capacitance may be correlated or used to estimate a deflection in the cover glass resulting from the applied force. In another embodiment, as described with respect to FIG. 6, the force-sensing circuit estimates an amount of tilt applied to the cover glass based on a signal or signals received from one or more force sensors. In yet another embodiment, as described with respect to FIG. 7, the force-sensing circuit is used to detect a change in capacitance between capacitive sensors (or with respect to a single sensor, in a self-capacitance mode) at a set of distinct locations below the cover glass. The change in capacitance can be used to estimate the displacement on the cover glass resulting from the applied force.

At operation 1115, the location of the one or more touches is determined. In one example, the force-sensing circuit determines one or more locations at which the force is being applied to the cover glass element based on the signal or signals received from one or more force sensors. The location may be determined by, for example, comparing the output from multiple force sensors and using the output to triangulate or estimate a location of the applied force.

At operation 1120, the amount or magnitude of the force being applied at each location is estimated. For example, the force-sensing circuit may be used to determine an amount or magnitude of force being applied at each measured location, such as using the weighted centroid technique described with respect to the FIG. 8. In some embodiments, the operations of method 1100 are repeated multiple times. In some embodiments, the operations of method 1100 are repeated so long as the force sensitive device is powered on.

FIG. 11B depicts another process for operating a device having a force sensor. The process may be applied using the force sensors described above with respect to FIGS. 2A, 2B, 3-8, discussed above.

FIG. 11B depicts another exemplary flow chart for a process 1150 that includes flow points and operational steps or functions. Although these flow points and operations are shown in a particular order, in the context of a more generalized technique, there is no particular requirement that the order of the operations must be followed as shown. Similarly, although these flow points and operations are shown performed by a general purpose processor in a device, in the context of a more generalized approach, there is no particular requirement for any such limitation. In some cases, prior to performing the operations of process 1150, the electronic device has been turned on and the operating system has been loaded and is running. Also, the relevant hardware including, for example, touch screen sensors, display devices, and force sensor devices may have been powered and may have been initialized.

At operation 1155, a charge signal is transmitted to a force-sensitive structure. In a typical implementation, the charge signal includes a series of charge pulses is transmitted to one of the capacitive plates in a force-sensitive structure. Each charge pulse comprises a momentary change in the voltage applied to the capacitive plates of the force-sensitive structure resulting in an induced current across the plates. In some instances, the charge signal is an alternating current (AC) that is applied across the capacitive plates of the force-sensing structure. In many cases, if the charge signal is a discrete charge pulse, the charge pulse is transmitted at regular intervals during the operation of the device. If the charge signal is an alternating current, the charge signal may be transmitted continuously during operation. In either case, operation 1155 is typically performed simultaneously with operations 1160, 1165, and 1170, described below.

At operation 1160, a first capacitance is measured for the force-sensitive structure. Typically, the capacitance is measured while the force-sensitive structure is in an uncompressed or unactuated state. For example, the measurement of operation 1160 may be taken when the device is stationary and is not being touched by an operator. In some cases, multiple measurements are taken over a period of time and a composite or average capacitance value is determined.

At operation 1165, a force is applied to the device. In accordance with the embodiments described above with respect to FIGS. 2A, 2B, 3-8, a user may touch the cover glass of a device applying a force at a location on the cover glass. The user may touch the device with a finger, stylus, pen, or the like. In some cases, multiple touches are applied to the cover glass at the same time in accordance with a multi-touch gesture or user input. In accordance with the embodiments described above with respect to FIGS. 2A, 2B, 3-8, an applied force typically results in the compression or deflection of a force-sensitive structure resulting in a relative change in position of the two capacitive plates.

At operation 1170, a second capacitance is measured for the force-sensitive structure. Typically, the capacitance is measured while the force-sensitive structure is in a compressed or deflected state due to the force applied in operation 1165, described above. In some cases, multiple measurements are taken over a period of time and a composite or representative capacitance value is determined.

At operation 1175, a force is estimated using the first and second capacitance measurements. In accordance with the embodiments described above with respect to FIGS. 2A, 2B, 3-8, an applied force results in a change in the position of the two capacitive plates, thus changing the capacitance of the force-sensitive structure. In operation 1175, the change in capacitance is correlated with or used to compute an estimated force. For example, if compressible element of a force-sensitive structure behaves as a linear force spring, the change in capacitance (which is proportional to the change in distance between the capacitive plates) will be proportional to the change in force. Because the material properties, such as the spring rate, of the compressible element are known the amount of force can be estimated as the difference between the first and second capacitance measurements multiplied by a constant. In some embodiments, the operations of method 1150 are repeated multiple times. In some embodiments, the operations of method 1150 are repeated so long as the force sensitive device is powered on.

6. Electrical Connection to a Force Sensor and Method of Manufacturing

In accordance with certain embodiments described above, a capacitive force sensor typically includes a force-sensitive stack having two capacitive plates separated by an intermediate, compressible element. In a typical implementation, a charge signal is applied to at least one of the capacitive plates and a capacitive measurement is taken. To deliver both the charge signal (drive signal) and receive the capacitive measurement (sense signal) from the capacitive plates, the force-sensitive structure is typically connected to other elements of the system by an electrical connection. To facilitate assembly during manufacturing, it may be advantageous that the electrical connection be a detachable electrical connection formed from a flexible conduit.

FIG. 12 depicts an example touch device 1200 having two force-sensing structures 1210, 1220 located around the perimeter of a display element 1202 or a portion thereof. The two force-sensing structures 1210, 1220 are electrically connected to an electrical connector tail 1250. In this example, each of the two force-sensing structures (1210, 1220) is formed from a first and second capacitive plate separated by an intermediate, compressible element. Generally, the force-sensing structures 1210 and 1220 can be used to determine a magnitude of a touch on a surface of the device. As explained above with respect to FIGS. 3-5, a force applied to the device compresses or deforms the compressible element, changing the distance between the first and second capacitive plates. The change in distance can be measured as a change in capacitance between the two plates using force-sensing circuitry. Accordingly, the two structures 1210, 1220 cooperate to sense a force; in this manner, they may be referred to as either separately or together as a “force-sensing structure.”

The electrical connector tail 1250 can be used to electrically couple the two force-sensing structures 1210, 1220 with the force-sensing circuitry, which may be located on a separate circuit component within the device. In some cases, it may be advantageous that the electrical connector tail 1250 is formed from a flexible conduit to facilitate connection with the force-sensing circuitry. For example, the electrical connector tail 1250 may be formed from a laminate of polyimide materials that have been printed or formed with electrical conductive traces. In some cases, it may be further advantageous that the flexible conduit be configured to bend easily to facilitate routing within the limited space of the device enclosure. To improve the flexibility or bend radius of the connector tail 1250, it may be advantageous to eliminate or remove the intermediate, compressible element in at least an end portion of the connector tail 1250. Removing the intermediate, compressible element may also facilitate electrical connection with one or more internal surfaces of the electrical connector tail 1250.

FIG. 13 depicts a cross-sectional view along line 3-3 of the electrical connector tail 1250. As shown in FIG. 13, the electrical connector tail 1250 is formed from four circuit layers 1211, 1212, 1221, 1222. In this example, each of the circuit layers includes at least one flexible dielectric layer and at least one flexible conductive layer. The flexible dielectric layer may be formed from a polyimide sheet and the electrical conductive layer may be formed from a metal film or metallized trace material. Further, in this example, each of the circuit layers is electrically connected with a capacitive plate of one of the force-sensitive structures 1210, 1220 (depicted in FIG. 12). For example, the electrical conductive layer of circuit layer 1211 may be electrically connected to a first (upper) capacitive plate of the force-sensitive structure 1210. Similarly, the electrical conductive layer of circuit layer 1212 may be electrically connected to a second (lower) capacitive plate of the force-sensitive structure 1210. Similarly, the circuit layers 1221 and 1222 are electrically connected to a first (upper) and a second (lower) capacitive plate, respectively, of the force sensitive structure 1220. In this example, each of the circuit layers 1211, 1221, 1222, and 1212 are electrically coupled to a respective terminal 1213, 1223, 1224, and 1214.

Alternatively, one or more of the circuit layers 1211, 1221, 1222, and 1212 may serve as a ground layer for the force-sensitive structure 1210. In one example either of both of the outer circuit layers 1211 or 1212 are held at a constant voltage during the operation of the sensor to act as an electromagnetic shield. In some cases, the outer circuit layers 1211 or 1212 are connected to ground during the operation of the sensor to facilitate electromagnetic shielding. One or more of the outer circuit layers may serve as a ground shield, depending on the location of the source of the interference. In some cases, one or more additional ground shield circuit layers are added to the force-sensitive structure. These additional ground shield layers may be added, for example, to the outer surfaces of the outer circuit layers 1211 and 1212. In one example, the conductive traces in any ground shield layer may extent substantially across the entire surface of the circuit layer to maximize the area that is shielded by the ground shield layer.

As shown in FIG. 13, the two circuit layers 1211 and 1221 are separated from the other two circuit layers 1212, and 1222 by the intermediate compressible layer 1230. In this example, the compressible layer 1230 serves as the compressible element in the force sensors 1210, 1220. As also shown in FIG. 13, the compressible layer 1230 does not extend into an end portion 1255 of the electrical connector tail 1250. As shown in FIG. 13, a void region 1350 is formed between the pairs of circuit layers. In some embodiments, the tail may lack any intermediate compressible layer.

As explained above, this configuration may be advantageous from a few aspects. First, because there is no material connection between the upper and lower pairs of circuit layers, the bendability of the electrical connector tail 1250 is improved, which may facilitate a smaller bending radius. Additionally, because there is no material between the pairs of circuit layers, additional internal electrical terminals 1223 and 1224 may be used for electrical connections. This reduces the need for circuit vias or additional electrical routing that may otherwise be required to electrically connect the electrical conductive layers of internal circuit layers 1221, 1222 to an external terminal.

The tail 1250 may extend from the force-sensing structures 1210, 1220 and bend one or more times to connect to a flex or other electrical connection within the device. As one non-limiting example, the tail 1250 or, more appropriately, the flexible dielectric and flexible conductive layers may bend in a serpentine fashion to each an interconnect. Two separate structures may form the tail; each such structure may be formed from one flexible dielectric and one flexible conductive layer. Generally, the two tail structures may follow different paths insofar as one extends from the upper force-sensing structure 1210 and one from the lower force-sensing structure 1220. Nonetheless, the constituent structures of the tail 1250 are typically routed such that they do not experience any force exerted on a cover glass, housing or other external force-sensitive surface. Thus, the tail 1250 may not present a secondary path for an exerted force to bypass the force sensor which, in turn, may increase the accuracy of the force sensor. Likewise, other components of the electronic device may be structured such that they do not absorb or divert force exerted against a force-sensitive surface of the electronic device.

While the device 1200 depicted in FIG. 12 includes two force-sensing structures located around the periphery of a display element 1202, an alternative embodiment may include only a single force-sensing structure. In this case, the electrical connector tail may only include two conductive layers (on two circuit layers). In other alternative embodiments, a device may include more than two force-sensing structures and the electrical connector tail may have multiple conductive layers to facilitate connection with each of the force-sensing structures.

FIG. 14 depicts an example process 1400 for manufacturing a force sensor having an electrical connector tail. The process 1400 can be used to manufacture the force sensors 1210, 1220 having an electrical connector tail 1250 in accordance with the embodiments of FIGS. 12 and 13. The process 1400 may also be used to manufacture force sensors having a variety of configurations, including configurations having a single pair of conductive layers.

In operation 1405, a first circuit layer is obtained. In this example, the first circuit layer comprises at least a first flexible conductive layer and a first flexible dielectric layer. With reference to FIG. 13, the first circuit layer may include one of either of the circuit layers pairs 1211, 1221 or 1222, 1212. In some cases, the first circuit layer may be obtained by forming the first conductive layer on the first dielectric layer. The conductive layer may be formed by, for example, bonding a metal foil to a surface of the first dielectric layer. In some cases, the conductive layer may be formed by a deposition or sputtering process that deposits a conductive material onto the dielectric layer. In one example, the conductive layer also forms one or more of the capacitive plates used for the force sensor. In some cases, the first circuit layer is pre-manufactured and obtained as a sheet or die-cut component.

In operation 1410, a second circuit layer is obtained. In this example, the second circuit layer also comprises at least a second flexible conductive layer and a second flexible dielectric layer. With reference to FIG. 13, the second circuit layer may also include one of either circuit layer pairs 1211, 1221 or 1222, 1212 (that is also separated from the first circuit layer by the intermediate compressible layer 1230). As described above, the first circuit layer may be obtained by forming the first conductive layer on the first dielectric layer by laminating a metal foil or depositing a conductive material onto a surface of the dielectric layer. The second circuit layer may also be pre-manufactured as a sheet or die-cut component.

In operation 1415, a laminate structure is formed. In particular, a laminate structure is formed such that the compressible layer is disposed between the first and second circuit layers. With reference to FIG. 13, an exemplary laminate structure includes the four circuit layers 1211, 1221, 1222, 1212 and the compressible layer 1230. In many cases, other layers are formed as part of the laminate structure. For example, additional circuit layers, adhesive layers, and coatings may be formed as part of the laminate structure. In particular, an adhesive layer is typically used to bond the intermediate compressible layer with the other, adjacent components of the laminate structure. It is not necessary that either the first or second circuit layers (obtained in operations 1405 and 1410) be immediately adjacent or bonded directly to the compressible layer.

Operation 1415 may be performed by, for example, placing pressure sensitive adhesive (PSA) layers between the components of the laminate structure. The laminate may then be subjected to a pressing operation to bond the layers. In some cases, heat or other curing techniques may be employed to bond the layers together. In some embodiments, the PSA may be applied, all layers bonded, and then the structure die cut to its final form.

Operation 1415 may also be performed using an injection or insertion molding process. In this case, the first and second circuit layers may be laminated or pre-formed with other layers or components. The layers may then be placed in opposite halves of an injection mold cavity and the intermediate compressible layer may be formed between the layers by injecting a molten or liquid material into the injection mold. In one example, a spacer element is placed between the first in second circuit layers to hold the first and second circuit layers against the respective halves of the injection mold. The spacer element may be approximately the same thickness as the final dimension of the compressible layer. In one example, the spacer element is compressible and is slightly larger than the final dimension of the compressible layer to be injection molded between the first and second circuit layers. In this case, the spacer element exerts a force against the first and second circuit layers, which are pressed against respective cavity walls of the injection mold. By pressing the circuit layers against the cavity walls, the injected molded material is more likely to fill the area between the circuit layers rather than filling an area between the circuit layers and the cavity walls. In one example, multiple spacer elements are used, each spacer element formed from a semi-circular ring. The spacer elements may be placed near the injection point of the mold, which is typically near the center of the part. The spacer elements can then be removed by die-cutting the center portion of the part, which may also facilitate the creation of a viewing area for the display.

As part of operation 1415, one or more electrical vias may be formed between the various layers of the laminate structure. In some cases, electrical vias are formed through the compressible layer to connect circuit layers that are disposed on opposite sides of the compressible layer. The vias may be formed by, for example, the addition of conductive pillar elements that electrically connect the conductive layers of different circuit layers. Additionally or alternatively, conductive regions within the compressible layer may be formed and then reflowed or otherwise electrically connected with conductive layers of the laminate structure.

In some cases, the laminate structure that is formed in operation 1415 is cut to form the force sensor having an electrical connector tail. For example, if the first and second circuit layers (obtained in operations 1405 and 1410) are formed as a solid sheet of material, the laminate structure may be die cut to form the desired geometric profile features of the force sensor. Specifically, a center portion may be cut out of the middle of the laminate structure to facilitate installation with a display element. Thus, the display element will be visible through the hole created in the middle of the laminate structure. As mentioned above, if the laminate structure includes spacer elements used for an injection molding process, they may be removed by this die cutting operation. Additional cuts may be performed to form the connector tail portion of the force sensor.

The cutting operation may be optional if, for example, the first and second circuit layers (obtained in operations 1405 and 1410) have been pre-cut or have been formed in the desired geometric profile shape. In this case, operation 1415 may also include an indexing operation to align the layers of the laminate structure.

In operation 1420, a portion of the compressible layer is removed from the laminate structure. In this example, a portion of the compressible layer located in an end portion of electrical connector tail is removed from the laminate structure leaving a void region between the first and second circuit elements. As explained above with respect to FIGS. 12 and 13, removal of the compressible layer may improve the flexibility or bendability of the laminate structure. It may also provide access to terminals or electrical connections on circuit layers that are internal to the laminate structure.

Removing the compressible layer may be accomplished using one or more techniques. In a first example, the compressible layer is perforated or pre-cut near the end portion of the electrical connector tail. Also, within the end portion of the electrical connector tail, the pressure sensitive adhesive or other bonding layer may be omitted between the compressible layer and the adjacent layers of the laminate structure. In this case, the pre-cut or perforation and the absence of a bonding layer allows the portion of the compressible layer in the end portion of the electrical connector tail to be removed.

In a second example, one or more layers of the laminate structure are delaminated or stripped from the compressible layer exposing the compressible layer. In this case, as secondary cut operation may be performed to remove the portion of the compressible layer in the end portion of the electrical connector tail.

In a third example, the compressible layer may be cut from the end portion of the electrical connector tail without first delaminating or stripping layers of the laminate structure. For example, the portion of the compressible layer within the end portion of the connector tail may be removed by passing a knife or cutting implement between the layers of the laminate structure.

As an alternative to operation 1420, the laminate structure may be formed such that the end portion of the electrical connector tail does not include the compressible layer. For example, if the laminate structure is formed using an injection or insertion molding process, an insert mold element may be placed in the end portion of the electrical connector tail preventing the formation of a compressible layer in this region. In this case, the laminate structure is formed with a void region between the first and second circuit layers.

As described above, the process 1400 may also be used to manufacture force sensors having a variety of configurations, including configurations having a single pair of conductive layers. For example, a force sensor having only two circuit layers (one on each side of the intermediate compressible layer) may be formed using process 1400. Alternatively, a force sensor having multiple circuit layers formed on either side of the intermediate compressible layer may also be formed using process 1400.

The operations of process 1400 are provided as one example. However, a force sensor may also be formed by omitting one or more of the operations described above. For example, depending on how the laminate structure is created, it may not be necessary to perform operation 1420 to remove a portion of the compressible layer.

In certain embodiments, the tail may be connected to a flex, circuit board or other electronic contact. In some embodiments, the entire force-sensing structure may be placed into an oven to bond the tail to the electrical contact through, for example, a surface-mount technology (SMT) process. In some embodiments, the SMT process may heat the tail (or portions thereof) and/or the electrical contact to 200 degrees or more. This elevated temperature may have deleterious effects on the silicone of the force-sensing structure, however. Thus, the force-sensing structure may be placed in a heat-resistant envelope, pouch or other container with the tail extending outwardly therefrom. Thus, when the oven is heated for the SMT process, the tail may be heated to the appropriate temperature while the silicone and other layers of the force-sensing structure may be maintained at a temperature that does not cause damage. Further, it should be appreciated that the force-sensing structure may not be singulated or cut into its final form prior to heating in the oven.

FIG. 15A depicts another embodiment 1500 of a force-sensing electronic device. Similar to other embodiments described herein, the embodiment 1500 may include and electronic device having a cover 1505 positioned over a display stack 1515, which may be configured to detect the touch of a force on the surface of the cover 1505. The cover 1505 may be formed from a variety of materials including, for example, glass, polycarbonate or other plastic, sapphire and the like. The display stack 1515 may include a liquid crystal display (LCD), organic light omitting diode (OLED), or other electronic display component.

In some embodiments, the cover 1505 may move with respect to the housing 1510. When a force is exerted on the cover 1505, by, for example, the touch of a user, the cover 1505 may travel downwardly. It should be appreciated that the entirety of the cover 1505 may travel in such a fashion, rather than only deflecting locally while edges of the cover 1505 remain substantially immobile. Whether the cover 1505 deflects locally or not may depend on the relative stiffness of the cover 1505 and the components/elements positioned below the cover 1505.

In some embodiments, the downward travel of the cover 1505 likewise moves the display stack 1515 downward, which in turn may impact and/or compress a sheet sensor 1520 positioned beneath the display stack 1515. The sheet sensor 1520 may include a capacitive-plate type force sensor, strain gauge sensor, or other force-sensitive sensor, and may generally be referred to as a force sensing structure, sensor, or sheet sensor. In general, the sheet sensor 1520 may extend over a substantial portion of the display stack 1515. In some cases, the sheet sensor 1520 is formed from an array or series of force-sensing elements that are disposed throughout the area of the sheet sensor 1520.

As shown in FIG. 15A, the sheet sensor 1520 may substantially abut the display stack 1515. In some embodiments, the sheet sensor 1520 may be separated therefrom by an air gap and/or other components or layers in certain embodiments. In some embodiments, the sheet sensor 1520 may be affixed directly to an element of the display stack 1515.

The sheet sensor 1520 may be supported by a plate 1525 positioned below the sensor 1520 opposite the side facing the display stack 1515. In some embodiments the plate 1525 may be rigid or substantially rigid, while in other embodiments the plate 1525 may be flexible. Typically, although not necessarily, the sheet sensor 1520 is affixed to the plate 1525. In some embodiments, the plate 1525 may be fixed relative to the housing 1510 of the device. In some embodiments, the plate 1525 may be a mid-plate providing structural support and/or stiffness to the housing 1510 of the electronic device 1500, while in other embodiments the plate 1525 may be used primarily or solely to support the sheet sensor 1520. In still other embodiments, other electronic components (not shown) may share the plate 1525 with the sheet sensor 1520.

As the cover 1505 and display stack 1515 move downward, the sheet sensor 1520 may be compressed. This compression may be sensed by the sheet senor 1520 and a corresponding output generated. For example, the sheet sensor 1502 may have first and second capacitive plates or arrays 1530, 1535 (as used herein, the term “plate” is intended to cover an array as well) defining an upper surface and a lower surface of the sheet sensor, or otherwise positioned in an upper and lower region of the sensor. The first and second capacitive plates 1530, 1535 may be separated from one another by a compressible inner layer 1540, such as silicone or a compliant gel or polymer.

In some embodiments, the first and second capacitive plates 1530, 1535 are operatively coupled to a sensing circuit that is configured to estimate the force of a touch on the cover based on a change in capacitance between the first and second capacitive plates 1530, 1535. In some implementations, sensing circuit is configured to generate a drive signal or electrical current that is used to detect and measure changes in capacitance between the first and second capacitive plates 1530, 1535. As the first capacitive plate 1530 moves toward the second capacitive plate 1535, the reduction in distance may correspond to a change in capacitance between the plates, which may be correlated to the force exerted on the cover 1505.

It should be appreciated that the sheet sensor 1520 may operate as a self-capacitance or mutual capacitance sensor to measure force in this fashion. Accordingly, in a mutual capacitance configuration, one of the first and second capacitive plates may be a drive plate and the other may be a sense plate. In a self-capacitance configuration, one of the first and second plates maybe a ground or shield layer while the other is a sense plate. Further, one or both plates of the sheet sensor 1520 may be formed in a pixel pattern (as may the sheet sensor 1520 itself) in order to locally register the application of a force and provide a localized region at which a force is applied.

In an embodiment having a flexible or deflectable plate 1525 supporting the sheet sensor 1520, changes in capacitance may still be measured so long as the layers of the sheet sensor 1520 compress, even if the plate 1525 itself flexes. Similarly, in embodiment having an air gap between the sheet sensor 1520 and display stack 1515, a force of a touch may not be sensed until the display stack moves far enough to compress or impact the sheet sensor.

It should be appreciated that the sheet sensor 1520, as shown in FIG. 15A, need not be transparent insofar as it is located beneath the display stack 1515. Further, such a configuration may be suitable not only for use with a display stack having an LED or LCD display, but also with a display stack incorporating an OLED display layer.

FIG. 15B depicts an alternative embodiment 1500B of the embodiment shown in FIG. 15A. In this embodiment 1500B, foam 1545 or other compliant material or compliant layer may be placed between the display stack 1515 and sheet sensor 1520. The foam 1545 may generally stiffen the display stack 1515 and/or cover 1505 and thus prevent the entire stack/glass from moving downward. Instead, when a force is exerted on the cover 1505, the foam 1545 may deform locally and thereby concentrate the deformation and/or force in a localized region, which may in turn enhance the force-sensing capabilities of the embodiment 1500B. It should be appreciated that any suitable material may be placed between the display stack 1515 and the sheet sensor 1520; foam is but one example material.

In some embodiments, a compliant environmental seal 1501 may be positioned between the cover 1505 and housing 1510. The compliant gasket may prevent the ingress of dirt, dust and the like into the interior of the electronic device 1500B, but may still permit downward travel of the cover 1505 and display stack 1515. In alternative embodiments, the gasket 1550 may be relatively rigid and may cooperate with the foam 1545 (or operate in the absence of the foam 1545) to restrict downward motion of the cover 1505 at one or more edges, with the net result that the cover may deflect locally instead of traveling as a whole. Force may still be sensed in such an embodiment through localized compression of the sheet sensor 1520.

In some embodiments, a portion or all of the region occupied by the gasket 1550 may be coated with an oleophobic material. The oleophobic material may serve as a barrier against, or repel, oils, dust, dirt and other similar materials from entering the housing 1510 and/or impacting the force-sensing structure 1520. In this fashion the coating may serve to maintain operation of the force-sensing structure over time. Coatings other than an oleophobic coating may be used; other dust- and/or oil- and/or dirt-repellent coatings may be used in different embodiments.

FIG. 15C depicts still another embodiment of a force-sensitive electronic device 1500. This embodiment is generally similar to that of FIG. 15B, except for the structure of the sheet sensor 1520C. Here, the sheet sensor 1520C may be patterned from one or more strain gauges rather than taking the form of a capacitive sensor. Individual strain gauges may be arranged in an array, grid, or other pattern to form the sheet sensor 1520C. The strain gauges may be formed from a material that changes electrical properties or produces an electrical response due to a deflection of the sheet sensor 1520C. The strain gauges may be formed, for example, from a resistive material, piezoelectric resistive material, piezoelectric material, and the like. The strain gauges may also be formed as an array of strain gauge elements, each element comprised of a series of traces or patterns that may be configured to detect a localized strain or deflection.

As force is exerted on the cover 1505, it is transferred through the display stack 1515, through the foam 1545 (or other compliant layer), and to the strain gauge(s) of the sheet sensor 1520C. The strain gauges may experience an increase in strain due to the exerted force; this increase in strain may be correlated to determine the magnitude of the exerted force as generally described elsewhere herein. In some embodiments, the sheet sensor 1520C is operatively coupled to sense circuitry that is configured to monitor and detect changes in an electrical property or measure and electrical response of the strain gauges of the sheet sensor 1520C. For example, the sense circuitry may be configured to detect a change in resistance and/or charge due to a deflection of the sensor sheet 1520C.

In the embodiments shown in FIGS. 15A-15C, the cover and display stack are generally free to translate with respect to the housing. In some embodiments, the cover and/or display stack may be adhered to the housing or otherwise fixed with respect to the housing, such that force exerted on the cover causes local deformation of the cover rather than translation. In such embodiments, force may be relatively localized insofar as the boundary conditions of the cover prevent motion. Since the cover may still deflect locally, a force may still be transmitted through the various layers and sensed by the force sensor (e.g., the sheet sensor).

FIG. 15D depicts a close-up of area 15D in FIG. 15C, showing one embodiment of a compliant layer 1545D positioned between the sheet sensor 1520 and the base of the display stack 1515. In the cross-sectional view of the electronic device 1500 shown in FIG. 1, the compliant layer 1545D is formed from a series or array of pillar-like structures 1560 sandwiched between an upper compliant substrate 1555 and a lower rigid substrate 1565 made of glass or the like. (In some embodiments, the lower substrate may also be compliant). In certain embodiments, the upper sheet 1555 may be formed from silicone, as may the pillar structures 1555. A sheet sensor 1520C is located beneath the lower substrate 1565. In the present embodiment, the sheet sensor 1520C is formed of one or more strain gauges, as discussed above with respect to FIG. 15C. The sheet sensor 1520C may be supported by a sense plate 1525, as generally discussed above.

In some implementations, the pillar structures 1555 may deform under downward pressure exerted on the compliant layer 1545C by the display stack 1515, or any other element of the electronic device 1500C that exerts pressure on the compliant layer 1545D. One or more void spaces 1550 may be defined between and/or around the pillars 1560. For example, adjacent pillars 1560 may be separated by a void space 1550 and each void space 1550 may be separate and distinct. As another option, a single void space 1550 may encompass all the pillars 1560. Different configurations of void spaces and pillar structures are thus contemplated.

As the pillar structures 1555 deform, the top sheet 1555 moves closer to the bottom sheet 1565 and the resistance of the pillar structure to further collapse increases. Further, the strain exerted on the sheet sensor 1520C through the compliant layer 1545D generally increases, causing the strain gauge output to increase. This increase in output may be correlated to a force exerted on the exterior of the housing.

In some embodiments, the void space or spaces 1550 may be filled with an optically transparent or near-transparent fluid, gel or the like (collectively, “fluid”). In some embodiments, the fluid may be optically indexed matched to the optical index of the pillar structures. That is, in certain embodiments, the index of refraction of the fluid may match or approximate that of the pillar structures 1555. In such an embodiment, the combination of fluid in the void spaces 1550 and pillar structures 1560 may render the compliant layer 1545D optically transparent and/or near-invisible. This may be useful when the display is an OLED display, for example.

In yet another embodiment and as shown in FIG. 15E, the compliant layer 1545D may separate a lower capacitive sensing array 1570 from an upper capacitive sensing array 1575. In such an embodiment 1500E, the capacitive sensing arrays 1570, 1575 may operate as described elsewhere herein, such that one array is a drive array (or reference array) and one is a sense array. The compliant layer 1545D may serve to prevent the two layers from approaching too close to one another and thus prevent, or at least reduce the likelihood of, contact between the two layers and/or excessive capacitive coupling between the two layers, which may result in inaccurate force measurement.

FIG. 16 depicts a partial cross-section of another embodiment of a force-sensing electronic device 1630. This embodiment may include a force-sensing structure 1600 similar to that shown in FIGS. 2A and 3, and described elsewhere herein. For example, the force-sensing structure 1500 may be configured with multiple capacitive layers separated by a deformable middle body, as generally discussed with respect to FIG. 3 and/or the variants shown in FIGS. 4-6. The force-sensing structure 1600 may take the form of a gasket any may be located between the cover 1505 and a housing 1510. In one embodiment, the portion of the housing 1510 adjacent the cover 1505 may include a bezel or bezel portion.

The force-sensing structure 1600 may extend partly or fully about a perimeter of the electronic device, cover, and/or portion of either. Alternately, multiple force-sensing structures 1600 may cooperate to extend partly or fully about a perimeter of the electronic device 1630, cover, and/or portion of either. In some embodiments, the force-sensing structure 1600 may be configured to prevent the ingress of contaminants into the interior of the housing 1510 and, therefore, may also function as a gasket. In some cases, the combination gasket and sensor is referred to as a strain-sensitive gasket or gasket force-sensing structure.

As with prior embodiments, the force-sensing structure 1600 may capacitively sense a distance between the first and second plates 1620, 1625 or other sensor structures; the output of the force-sensing structure 1600 may be correlated to a force by a sensing circuit, processor, or other electronic component of the force-sensing electronic device 1630. In some embodiments, the force-sensing structure 1600 is operatively coupled to sense circuitry that is configured to detect and measure changes to an electrical property of the force-sensing structure 1600, which may be correlated to the force of a touch on the cover 1505.

In addition to the force-sensing structure 1600 generally positioned between the cover 1505 and bezel or housing 1510, the present embodiment may incorporate a force-sensitive sheet sensor 1520. The sheet sensor 1520 is generally similar in configuration and operation to any of the sheet sensors described above with respect to FIGS. 15A-15D.

As shown in FIG. 16, the sheet sensor 1520 may be separated from the display stack by a small air gap. Additionally or alternatively, the sheet sensor 1520 may be separated from the display stack by a compressible layer similar to the compressible layer described above with respect to FIGS. 15B-E. When the cover 1505 and display stack 1515 deflect in response to a force, the gasket force-sensing structure 1600 may compress and sense force, as generally described herein. To prevent bottoming out of the cover and display stack when a force is applied away from the edges of the cover, the sheet sensor 1520 may be included. When the display stack and cover deform sufficiently, they may contact the sheet sensor 1520 and transmit force thereto. The two force sensors 1600 and 1520 may cooperate to determine a force. For example, the output of both force sensors may be taken and manipulated to determine the force exerted on the cover. In this manner, the dynamic force sensing range of the device 1500 may be extended to sense and react to forces that would otherwise be sufficiently large to cause the cover to bottom out and the single gasket sensor 1600 to register a maximum value. In some embodiments, the air gap is configured to at least partially collapse in response to a force of a touch that exceeds a first threshold. In some implementations, the first threshold is less than a second threshold that corresponds to a maximum force that can be practically or reliably detected by gasket force-sensing structure 1600.

FIG. 17 depicts yet another embodiment of an electronic device 1700 that may employ a sheet or pad sensor 1520 for capacitively measuring a force exerted on a cover 1505 (or, in other embodiments, a portion of a housing or a different type of input surface). Generally, the structure and operation of the sheet sensor 1520 is similar to that described herein with respect to prior figures.

In addition to the upper and lower capacitive arrays of the sheet sensor 1520, a second capacitive sense layer/array 1705 may be placed within the display stack 1515. In one embodiment, the second capacitive sense layer 1705 may be formed from indium-tin-oxide, silver nanowire, PEDOT, or any other suitable conductive material. In certain embodiments, it may be desirable for the second capacitive sense layer 1705 to be transparent.

In the embodiment 1700 of FIG. 17, the second capacitive sense layer 1705 may be placed relative to the display stack 1515. The capacitive sense layer 1705 may, in some instances, function as a capacitive touch sensor for sensing the location of a touch on the cover 1505. In some embodiments, the capacitive sense layer 1705 is positioned above a backlight unit 1710. If the second capacitive sense layer 1705 is transparent or nearly so, it may not interfere with the operation of the backlight unit 1710 and/or the remainder of the display stack 1515.

As shown in FIG. 17, an air gap may be located between the capacitive sense layer 1705 and the sheet sensor 1520. Additionally or alternatively, the sheet sensor 1520 may be separated from the capacitive sense layer 1705 by a compressible layer similar to the compressible layer described above with respect to FIGS. 15B-E.

As a force is exerted on the cover 1505 (or housing or input surface, in some embodiments), the cover and display stack 1515 are moved closer to the sheet sensor 1520. Thus, the second capacitive sense layer 1705 is likewise moved closer to the sheet sensor 1520. Accordingly, a capacitance between at least a portion of the second capacitive sense layer 1705 and the upper capacitive array 1530 of the sheet sensor 1520 may increase with such motion. Further, because the cover 1505, display stack 1515 and second capacitive sense layer 1705 may deform locally in response to the force, the capacitance may increase (or increase more) in the general region corresponding to the exerted force. This change in capacitance may be used to estimate the applied force, as generally described elsewhere herein.

Under sufficient force, the backlight unit 1710 (or other base of the display stack) will contact the upper surface of the sheet sensor 1520. Once this occurs, the capacitance between the second capacitive sense layer 1705 and the upper capacitive array 1530 of the sheet sensor 1520 will generally reach a maximum value. Additional force may cause the sheet sensor 1520 to compress, thereby moving at least a portion of the upper capacitive array 1530 closer to the lower capacitive array 1535 and increasing a capacitance between these two elements, at least within a given region. Thus, even though the capacitance between the second capacitive sense layer 1705 and the upper capacitive array 1530 may be at maximum or near-maximum value, the increase in capacitance between the arrays 1530, 1535 of the sheet sensor 1520 may be used to determine estimates of an exerted force.

In some embodiments, sensing circuitry is operatively coupled to the capacitive sense layer 1705 and the sheet sensor 1520. The sensing circuitry may be configured to estimate the force of a touch on the cover based on a change in mutual capacitance between the capacitive sense layer 1705 and the upper and/or capacitive plate of the sheet sensor 1520. In some embodiments, the sensing circuitry may be configured obtain a first capacitance between the upper capacitive plate and the lower capacitive plate of the sheet sensor and also obtain a second capacitance between the upper capacitive plate and the capacitive sense layer. An estimate of a force of a touch on the cover may be computed or generated using the first and second capacitances measured using the sensing circuitry.

It may be considered, then, that the capacitance between the second capacitive sense layer 1705 and the upper capacitive array 1530 may be used to determine or estimate an exerted force between zero and some first threshold value, and the capacitance between the upper and lower capacitive arrays 1530, 1535 of the sheet sensor 1520 may be used to determine an exerted force between the first threshold value and a second threshold value. This combination of sensing structures may provide force sensing about a wider range of values than may be achieved by the use of a single sensor.

It should be appreciated that embodiments described herein may measure changes in force, thereby providing a non-binary or even substantially continuous input to an associated electronic device, corresponding to changes in distance or less than 2 microns between two capacitive structures or arrays. Thus, although one or both of the capacitive structures or arrays may move with respect to the other, the motion may be imperceptible to a human interacting with the device. Changes in distance on the measure of nanometers may correspond to approximately one gram of force being exerted on a surface, as one non-limiting example.

While the present disclosure has been described with reference to various embodiments, it will be understood that these embodiments are illustrative and that the scope of the disclosure is not limited to them. Many variations, modifications, additions, and improvements are possible. More generally, embodiments in accordance with the present disclosure have been described in the context of particular embodiments. Functionality may be separated or combined in procedures differently in various embodiments of the disclosure or described with different terminology. These and other variations, modifications, additions, and improvements may fall within the scope of the disclosure as defined in the claims that follow. 

We claim:
 1. An electronic device, comprising: a cover; a display disposed within the electronic device and visible through the cover; a force-sensing structure disposed within the electronic device on one side of the cover, comprising: a first capacitive electrode; a second capacitive electrode; and a compressible element disposed between the first and second capacitive electrodes; and a sheet sensor positioned on a side of the display opposite the cover and configured to be engaged by the display when a sufficient force is applied at a region of the cover away from an edge of the cover, wherein: the force-sensing structure and sheet sensor have different force sensing ranges; at least before the display engages the sheet sensor, the force-sensing structure is configured to produce a first output corresponding to a capacitive change of the force-sensing structure, the capacitive change of the force-sensing structure indicating an amount of force applied to the cover; and after the display engages the sheet sensor, the sheet sensor is configured to produce a second output corresponding to a capacitive change of the sheet sensor, the capacitive change of the sheet sensor indicating the amount of force applied to the cover.
 2. The electronic device of claim 1, further comprising: a housing defining an opening, wherein: the cover is disposed over the opening; and the force-sensing structure forms a gasket between the housing and the cover.
 3. The electronic device of claim 2, wherein: the housing defines a bezel having a shelf surrounding the opening; and the force-sensing structure is positioned between the shelf and the cover.
 4. The electronic device of claim 1, wherein: the sheet sensor comprises: an upper capacitive layer; a lower capacitive layer; and a compressible layer disposed between the upper and lower capacitive layers; and the electronic device further comprises a plate affixed to and supporting the sheet sensor.
 5. The electronic device of claim 4, wherein an air gap is located between the display and the sheet sensor.
 6. The electronic device of claim 1, wherein the force-sensing structure comprises: a first force-sensing segment disposed under a first edge of the cover; and a second force-sensing segment disposed under a second edge of the cover; and the electronic device further comprises force-sensing circuitry operatively coupled to the first and second force-sensing segments and configured to: detect changes in capacitive coupling due to deflection of the first and second force-sensing segments; and produce a signal that corresponds to the amount of force applied to the cover.
 7. The electronic device of claim 1, wherein the force-sensing structure comprises: a first force-sensing segment disposed under a first edge of the cover, the first force-sensing segment comprising the first capacitive electrode, the second capacitive electrode, and at least a portion of the compressible element; a second force-sensing segment disposed under a second edge of the cover; a third force-sensing segment disposed under a third edge of the cover; and a fourth force-sensing segment disposed under a fourth edge of the cover.
 8. The electronic device of claim 1, wherein the compressible element comprises a compliant sheet having a center opening in which the display is positioned.
 9. The electronic device of claim 1, wherein the compressible element comprises multiple segments positioned around a center opening in which the display is positioned.
 10. An electronic device, comprising: a cover; a first force-sensing structure disposed under at least a first edge of the cover and comprising a first pair of capacitive elements separated by a compressible layer; a second force-sensing structure disposed under at least a second edge of the cover and comprising a second pair of capacitive elements separated by the compressible layer; and a sheet sensor positioned below the cover between the first and second force-sensing structures and configured to be engaged when a sufficient force is applied at a region of the cover away from an edge of the cover; wherein: the first and second force-sensing structures have a different force sensing range than the sheet sensor; at least before the sheet sensor is engaged, the first and second force-sensing structures are configured to produce first outputs corresponding to capacitive changes of the first and second force-sensing structures, the capacitive changes of the first and second force-sensing structures indicating an amount of force applied to the cover; and after the sheet sensor is engaged, the sheet sensor is configured to produce a second output corresponding to a capacitive change of the sheet sensor, the capacitive change of the sheet sensor indicating the amount of force applied to the cover.
 11. The electronic device of claim 10, further comprising: a third force-sensing structure disposed under at least a third edge of the cover and comprising a third pair of capacitive elements separated by the compressible layer; and a fourth force-sensing structure disposed under at least a fourth edge of the cover and comprising a fourth pair of capacitive elements separated by the compressible layer.
 12. The electronic device of claim 10, further comprising: a housing defining an opening having a shelf, wherein: the cover is positioned within the opening; and the first and second force-sensing structures are positioned on the shelf under the cover.
 13. The electronic device of claim 10, wherein the compressible layer comprises multiple compressible element segments.
 14. An electronic device, comprising: a housing defining an opening; a cover disposed over the opening; a touch sensor disposed within the electronic device on one side of the cover and configured to detect a location of a touch on the cover; a force-sensitive layer disposed within the electronic device on the one side of the cover; and a force-sensing structure disposed on a side of the force-sensitive layer opposite the cover; and a compressible layer located between the force-sensitive layer and the force-sensing structure; wherein: the force-sensing structure is configured to be engaged when a sufficient force is applied at a region of the cover away from an edge of the cover, the sufficient force causing the compressible layer to collapse; at least before the compressible layer collapses in response to an amount of force of the touch on the cover, the force-sensitive layer is configured to produce a first output corresponding to a capacitive change of the force-sensitive layer, the capacitive change of the force-sensitive layer indicating the amount of force; and after the compressible layer collapses in response to the amount of force, the force-sensing structure is configured to produce a second output corresponding to a capacitive change of the force-sensing structure, the capacitive change of the force-sensing structure indicating the amount of force.
 15. The electronic device of claim 14, further comprising a support structure fixed relative to the housing and supporting the force-sensing structure.
 16. The electronic device of claim 14, wherein: the force-sensitive layer comprises a capacitive electrode; the force-sensing structure comprises a first capacitive layer and a second capacitive layer separated by a second compressible layer; and the capacitive electrode of the force-sensitive layer is configured to capacitively couple to the first capacitive layer of the force-sensing structure.
 17. The electronic device of claim 16, wherein: the electronic device further comprises sensing circuitry operatively coupled to the force-sensing layer and the force-sensing structure; and the sensing circuitry is configured to estimate the amount of force applied to the cover based on a change in mutual capacitance between the capacitive electrode of the force-sensitive layer and the first capacitive layer of the force-sensing structure.
 18. The electronic device of claim 17, wherein the sensing circuitry is configured to: obtain a first capacitance between the first capacitive layer and the second capacitive layer of the force-sensing structure; obtain a second capacitance between the capacitive electrode of the force-sensitive layer and the first capacitive layer of the force-sensing structure; and generate an estimate of the amount of force of the touch on the cover using the first and second capacitances.
 19. The electronic device of claim 14, further comprising: a display disposed between the cover and the force-sensing structure, wherein: the compressible layer is located between the display and the force-sensing structure.
 20. The electronic device of claim 19, wherein: the force-sensitive layer has a different force sensing range than the force-sensitive structure. 